feat(contacts): Add 'Last Seen' timestamp display with activity indicators

Add comprehensive "last seen" tracking for all contact types:

Backend (cli.py):
- New function get_contacts_with_last_seen() using 'apply_to t=1,t=2,t=3,t=4 contact_info'
- Fetches detailed contact metadata including last_advert timestamps
- Returns dictionary indexed by full public_key for efficient lookup

API (api.py):
- Enhanced /api/contacts/detailed endpoint to merge last_seen data
- Matches contacts by public_key_prefix (first 12 chars)
- Graceful fallback if detailed fetch fails (contacts still displayed without last_seen)

Frontend (contacts.js):
- formatRelativeTime() - converts Unix timestamps to human-readable format
  ("5 minutes ago", "2 hours ago", "3 days ago")
- getActivityStatus() - returns status indicator based on recency:
  🟢 Active (< 5 min), 🟡 Recent (< 1 hour), 🔴 Inactive (> 1 hour)
- Contact cards now display "Last seen" with status icon and relative time
- Clean handling of missing last_seen data (shows "Unknown")

This feature helps users identify active vs. inactive contacts at a glance,
using the last_advert field from meshcli's contact_info command.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

app/meshcore/cli.py

@@ -524,6 +524,63 @@ def get_all_contacts_detailed() -> Tuple[bool, List[Dict], int, str]:
         return False, [], 0, str(e)
 
 
+def get_contacts_with_last_seen() -> Tuple[bool, Dict[str, Dict], str]:
+    """
+    Get detailed contact information including last_advert timestamps.
+
+    Uses 'apply_to t=1,t=2,t=3,t=4 contact_info' command to fetch metadata
+    for all contact types (CLI, REP, ROOM, SENS).
+
+    Returns:
+        Tuple of (success, contacts_dict, error_message)
+        contacts_dict maps public_key -> contact_details where each detail dict contains:
+        {
+            'public_key': str (full key),
+            'type': int (1=CLI, 2=REP, 3=ROOM, 4=SENS),
+            'flags': int,
+            'out_path_len': int,
+            'out_path': str,
+            'adv_name': str (name with emoji),
+            'last_advert': int (Unix timestamp),
+            'adv_lat': float,
+            'adv_lon': float,
+            'lastmod': int (Unix timestamp)
+        }
+    """
+    try:
+        # Execute command to get all contact types
+        # t=1 (CLI), t=2 (REP), t=3 (ROOM), t=4 (SENS)
+        success, stdout, stderr = _run_command(['apply_to', 't=1,t=2,t=3,t=4', 'contact_info'])
+
+        if not success:
+            return False, {}, stderr or 'Failed to get contact details'
+
+        # Parse JSON output
+        try:
+            # The output should be a JSON array
+            contact_list = json.loads(stdout)
+
+            if not isinstance(contact_list, list):
+                return False, {}, 'Unexpected response format (expected JSON array)'
+
+            # Build dictionary indexed by public_key for easy lookup
+            contacts_dict = {}
+            for contact in contact_list:
+                if 'public_key' in contact:
+                    # Use full public key as index
+                    contacts_dict[contact['public_key']] = contact
+
+            return True, contacts_dict, ""
+
+        except json.JSONDecodeError as e:
+            logger.error(f"Failed to parse contact_info JSON: {e}")
+            return False, {}, f'JSON parse error: {str(e)}'
+
+    except Exception as e:
+        logger.error(f"Error getting contact details: {e}")
+        return False, {}, str(e)
+
+
 def delete_contact(selector: str) -> Tuple[bool, str]:
     """
     Delete a contact from the device.

app/routes/api.py

@@ -1221,6 +1221,7 @@ def get_contacts_detailed_api():
                     "public_key_prefix": "df2027d3f2ef",
                     "type_label": "REP",
                     "path_or_mode": "Flood",
+                    "last_seen": 1735429453,  // Unix timestamp from last_advert
                     "raw_line": "..."
                 },
                 ...
@@ -1228,16 +1229,10 @@ def get_contacts_detailed_api():
         }
     """
     try:
+        # Get basic contacts list
         success, contacts, total_count, error = cli.get_all_contacts_detailed()
 
-        if success:
-            return jsonify({
-                'success': True,
-                'contacts': contacts,
-                'count': total_count,
-                'limit': 350  # MeshCore device limit
-            }), 200
-        else:
+        if not success:
             return jsonify({
                 'success': False,
                 'error': error or 'Failed to get contacts list',
@@ -1246,6 +1241,32 @@ def get_contacts_detailed_api():
                 'limit': 350
             }), 500
 
+        # Get detailed contact info with last_advert timestamps
+        success_detailed, contacts_detailed, error_detailed = cli.get_contacts_with_last_seen()
+
+        if success_detailed:
+            # Merge last_advert data with contacts
+            # Match by public_key_prefix (first 12 chars of full public_key)
+            for contact in contacts:
+                prefix = contact.get('public_key_prefix', '')
+
+                # Find matching contact in detailed data
+                for full_key, details in contacts_detailed.items():
+                    if full_key.startswith(prefix):
+                        # Add last_seen timestamp
+                        contact['last_seen'] = details.get('last_advert', None)
+                        break
+        else:
+            # If detailed fetch failed, log warning but still return contacts without last_seen
+            logger.warning(f"Failed to get last_seen data: {error_detailed}")
+
+        return jsonify({
+            'success': True,
+            'contacts': contacts,
+            'count': total_count,
+            'limit': 350  # MeshCore device limit
+        }), 200
+
     except Exception as e:
         logger.error(f"Error getting detailed contacts list: {e}")
         return jsonify({

app/static/js/contacts.js

@@ -523,6 +523,93 @@ function renderExistingList(contacts) {
     });
 }
 
+/**
+ * Format Unix timestamp as relative time ("5 minutes ago", "2 hours ago", etc.)
+ */
+function formatRelativeTime(timestamp) {
+    if (!timestamp) return 'Never';
+
+    const now = Math.floor(Date.now() / 1000); // Current time in Unix seconds
+    const diffSeconds = now - timestamp;
+
+    if (diffSeconds < 0) return 'Just now'; // Future timestamp (clock skew)
+
+    // Less than 1 minute
+    if (diffSeconds < 60) {
+        return 'Just now';
+    }
+
+    // Less than 1 hour
+    if (diffSeconds < 3600) {
+        const minutes = Math.floor(diffSeconds / 60);
+        return `${minutes} minute${minutes !== 1 ? 's' : ''} ago`;
+    }
+
+    // Less than 1 day
+    if (diffSeconds < 86400) {
+        const hours = Math.floor(diffSeconds / 3600);
+        return `${hours} hour${hours !== 1 ? 's' : ''} ago`;
+    }
+
+    // Less than 30 days
+    if (diffSeconds < 2592000) {
+        const days = Math.floor(diffSeconds / 86400);
+        return `${days} day${days !== 1 ? 's' : ''} ago`;
+    }
+
+    // Less than 1 year
+    if (diffSeconds < 31536000) {
+        const months = Math.floor(diffSeconds / 2592000);
+        return `${months} month${months !== 1 ? 's' : ''} ago`;
+    }
+
+    // More than 1 year
+    const years = Math.floor(diffSeconds / 31536000);
+    return `${years} year${years !== 1 ? 's' : ''} ago`;
+}
+
+/**
+ * Get activity status indicator based on last_seen timestamp
+ * Returns: { icon: string, color: string, title: string }
+ */
+function getActivityStatus(timestamp) {
+    if (!timestamp) {
+        return {
+            icon: '⚫',
+            color: '#6c757d',
+            title: 'Never seen'
+        };
+    }
+
+    const now = Math.floor(Date.now() / 1000);
+    const diffSeconds = now - timestamp;
+
+    // Active (< 5 minutes)
+    if (diffSeconds < 300) {
+        return {
+            icon: '🟢',
+            color: '#28a745',
+            title: 'Active (seen recently)'
+        };
+    }
+
+    // Recent (< 1 hour)
+    if (diffSeconds < 3600) {
+        return {
+            icon: '🟡',
+            color: '#ffc107',
+            title: 'Recent activity'
+        };
+    }
+
+    // Inactive (> 1 hour)
+    return {
+        icon: '🔴',
+        color: '#dc3545',
+        title: 'Inactive'
+    };
+}
+
 function createExistingContactCard(contact, index) {
     const card = document.createElement('div');
     card.className = 'existing-contact-card';
@@ -567,6 +654,38 @@ function createExistingContactCard(contact, index) {
     keyDiv.textContent = contact.public_key_prefix;
     keyDiv.title = 'Public Key Prefix';
 
+    // Last seen row (with activity status indicator)
+    const lastSeenDiv = document.createElement('div');
+    lastSeenDiv.className = 'text-muted small d-flex align-items-center gap-1';
+    lastSeenDiv.style.marginBottom = '0.25rem';
+
+    if (contact.last_seen) {
+        const status = getActivityStatus(contact.last_seen);
+        const relativeTime = formatRelativeTime(contact.last_seen);
+
+        const statusIcon = document.createElement('span');
+        statusIcon.textContent = status.icon;
+        statusIcon.style.fontSize = '0.9rem';
+        statusIcon.title = status.title;
+
+        const timeText = document.createElement('span');
+        timeText.textContent = `Last seen: ${relativeTime}`;
+
+        lastSeenDiv.appendChild(statusIcon);
+        lastSeenDiv.appendChild(timeText);
+    } else {
+        // No last_seen data available
+        const statusIcon = document.createElement('span');
+        statusIcon.textContent = '⚫';
+        statusIcon.style.fontSize = '0.9rem';
+
+        const timeText = document.createElement('span');
+        timeText.textContent = 'Last seen: Unknown';
+
+        lastSeenDiv.appendChild(statusIcon);
+        lastSeenDiv.appendChild(timeText);
+    }
+
     // Path/mode (optional)
     let pathDiv = null;
     if (contact.path_or_mode && contact.path_or_mode !== 'Flood') {
@@ -597,6 +716,7 @@ function createExistingContactCard(contact, index) {
     // Assemble card
     card.appendChild(infoRow);
     card.appendChild(keyDiv);
+    card.appendChild(lastSeenDiv);
     if (pathDiv) card.appendChild(pathDiv);
     card.appendChild(actionsDiv);