fix(regions): allow clearing the default region in Region Registry

Click the already-selected radio to clear the default; new
DELETE /api/regions/default endpoint also pushes an empty CMD 63 to
the firmware so its persistent default is wiped too.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/routes/api.py

@@ -4070,6 +4070,43 @@ def set_channel_scope_api(index):
         return jsonify({'success': False, 'error': str(e)}), 500
 
 
+@api_bp.route('/regions/default', methods=['DELETE'])
+def clear_default_region_api():
+    """Clear the default-region flag in the DB and the firmware default (CMD 63).
+
+    If the firmware push fails the DB flag is still cleared; we return 200 with
+    a non-blocking `warning` so the UI can toast it.
+    """
+    try:
+        db = _get_db()
+        if not db:
+            return jsonify({'success': False, 'error': 'Database not available'}), 500
+
+        had_default = db.get_default_region() is not None
+        db.set_default_region(None)
+
+        warning = None
+        if had_default:
+            dm = _get_dm()
+            if dm and dm.is_connected:
+                try:
+                    res = dm.set_default_flood_scope('', '')
+                    if not res.get('success'):
+                        warning = f"{res.get('error')} Your choice is saved locally."
+                except Exception as e:
+                    warning = f"Could not clear firmware default: {e}. Your choice is saved locally."
+            else:
+                warning = 'Device disconnected — choice saved locally; firmware default not updated.'
+
+        out = {'success': True}
+        if warning:
+            out['warning'] = warning
+        return jsonify(out), 200
+    except Exception as e:
+        logger.error(f"Error clearing default region: {e}")
+        return jsonify({'success': False, 'error': str(e)}), 500
+
+
 @api_bp.route('/regions/<int:region_id>/default', methods=['POST'])
 def set_default_region_api(region_id):
     """Mark a region as default in the DB AND push it to the firmware (CMD 63).

app/static/js/app.js

@@ -2871,7 +2871,8 @@ function renderRegionsList() {
                 <div class="form-check mb-0">
                     <input class="form-check-input" type="radio" name="regionDefault"
                            id="regionDefault_${r.id}" ${isDefault}
-                           onchange="setDefaultRegion(${r.id})">
+                           title="Click again to clear the default"
+                           onclick="handleRegionRadioClick(${r.id}, this)">
                 </div>
                 <div class="flex-grow-1">
                     <div><strong>${escapeHtml(r.name)}</strong></div>
@@ -2927,6 +2928,17 @@ async function deleteRegion(id, name) {
     }
 }
 
+function handleRegionRadioClick(id, inputEl) {
+    // Click on the already-selected default clears the default; otherwise sets it.
+    const wasDefault = (window.regionRegistry || []).some(r => r.id === id && r.is_default);
+    if (wasDefault) {
+        inputEl.checked = false;
+        clearDefaultRegion();
+    } else {
+        setDefaultRegion(id);
+    }
+}
+
 async function setDefaultRegion(id) {
     try {
         const resp = await fetch(`/api/regions/${id}/default`, { method: 'POST' });
@@ -2948,6 +2960,26 @@ async function setDefaultRegion(id) {
     }
 }
 
+async function clearDefaultRegion() {
+    try {
+        const resp = await fetch('/api/regions/default', { method: 'DELETE' });
+        const data = await resp.json().catch(() => ({}));
+        if (!resp.ok || !data.success) {
+            showNotification(data.error || 'Failed to clear default region', 'danger');
+            await loadRegions();  // snap UI back to server truth
+            return;
+        }
+        if (data.warning) {
+            showNotification(data.warning, 'warning');
+        }
+        (window.regionRegistry || []).forEach(r => { r.is_default = 0; });
+    } catch (e) {
+        console.error('Error clearing default region:', e);
+        showNotification('Network error clearing default', 'danger');
+        await loadRegions();
+    }
+}
+
 // ================================================================
 // Per-channel region picker (Manage Channels > row > pin icon)
 // ================================================================

app/templates/base.html

@@ -792,7 +792,7 @@
                                 </div>
                             </form>
                             <div class="form-text small">
-                                Tip: pick the default region via the radio button. The default is also pushed to the firmware so any untagged channel uses it.
+                                Tip: pick the default region via the radio button. Click the selected radio again to clear it. The default is also pushed to the firmware so any untagged channel uses it.
                             </div>
                         </div>
                     </div>