Add chat rooms, channels, sidebar nav, themes, and UI polish

Backend (profiles.py / main.py):
- Fix bot startup crash: create active user before start_chat
- Fix address-clobbering bug on restart (UserContactLink vs CreatedConnLink)
- Add user profile type alongside bots
- Channels: create groups with observer links, classify via acceptMemberRole
- Chat rooms: get_chat_history + send_to_chat, history/messages/send routes

UI:
- Chat room view with message bubbles and live polling
- Convert top nav to collapsible left sidebar (mobile-friendly off-canvas)
- Three-way Users/Bots split; clickable cards; copy-address buttons + links
- Add Matrix theme alongside Original Light/Dark
- File upload sidebar link; site footer on all pages incl. login
- Bot-type descriptions on the Bots page; QR caption on profiles

Remove orphaned index.html (superseded by list.html).
Ignore downloaded libs/, exploration DBs, and local ai.sh.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -10,3 +10,10 @@ __pycache__/
 *.pyc
 .venv/
 *.egg-info/
+
+# Downloaded libsimplex artifacts (regenerate via manager/download_sdk.sh)
+manager/libs/
+# Throwaway exploration databases
+manager/data/explore/
+# Local Claude session resume helper (machine-specific)
+manager/ai.sh