feat(dm): searchable contact selector, contact info modal, device-only contacts

Redesign DM chat contact selector:
- Replace <select> dropdown with searchable text input + filtered dropdown
- Show only device contacts (from /api/contacts/detailed), not all cached
- Sort contacts alphabetically, conversations by recency
- Type badge (CLI/REP/ROOM/SENS) shown in dropdown items
- Keyboard support: Enter selects first match, Escape closes

Add Contact Info modal (replaces Retry toggle in header):
- Shows contact name, type, public key, last advert, path/route, GPS
- Auto Retry toggle moved into modal footer
- Designed for future extensibility (manual path setting etc.)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/static/css/style.css

@@ -322,7 +322,7 @@ main {
 
     /* Navbar: Channel selector on mobile */
     #channelSelector,
-    #dmConversationSelector {
+    #dmContactSearchInput {
         min-width: 100px !important;
         font-size: 0.9rem;
     }