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Remove orphaned index.html (superseded by list.html).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>

manager/download_sdk.sh

@@ -0,0 +1,7 @@
+curl -L --progress-bar \
+  "https://github.com/simplex-chat/simplex-chat-libs/releases/download/v6.5.2/simplex-chat-libs-linux-x86_64.zip" \
+  -o /tmp/simplex-libs.zip && \
+unzip /tmp/simplex-libs.zip -d /tmp/simplex-libs-extracted && \
+mkdir -p ~/.cache/simplex-chat/v6.5.2/sqlite && \
+mv /tmp/simplex-libs-extracted/libs/* ~/.cache/simplex-chat/v6.5.2/sqlite/ && \
+echo "Done: $(ls ~/.cache/simplex-chat/v6.5.2/sqlite/)"