Phase 7: Bot/extension system

Bot accounts (User rows with is_bot=True), scoped API tokens (read:messages,
write:messages, manage:rooms) authenticated via Authorization: Bearer on both
REST and the WS handshake, live bot WebSocket access on the same /ws/chat
endpoint humans use, message editing (WS "edit" envelope -> message_update
broadcast, fans out cross-instance for free via the existing broadcaster),
incoming webhooks (room-scoped, no auth beyond the URL token), and outgoing
webhooks/event subscriptions (HMAC-SHA256 signed, backgrounded delivery,
creation-time SSRF validation against private/loopback/link-local targets).

Token auth is additive, not a parallel system: a bearer-token-authenticated
bot goes through the exact same room-membership/role checks a session-
authenticated human does everywhere; only read:messages/write:messages are
separately scope-gated (the two message endpoints). manage:rooms scope
enforcement, full per-delivery SSRF re-validation, and bot API rate limiting
were explicitly scoped out (confirmed with the repo owner) as disproportionate
to this phase -- documented as known gaps in backend/README.md rather than
silently skipped.

Admin portal gains a Bots tab (create bots, issue/revoke scoped tokens,
cross-room webhook visibility); RoomInfoPanel gains room-scoped webhook/
subscription management, mirroring how invites already work there. The chat
UI also gets a minimal "edit your own message" affordance -- not asked for
by the issue, but the only practical way to exercise the edit pipeline by
hand instead of only via a scripted bot client.

Along the way: fixed a real bug caught while writing the incoming-webhook
test -- offline-push notification relied on the sender being "connected" to
exclude themselves, true for WS-originated messages but not for the new
webhook path, which has no WS connection for the attributed sender at all.
Now explicitly excluded. Also discovered the REST-only test fixture never
triggered ASGI lifespan, so app.state.broadcaster/presence didn't exist for
it; moved their construction out of the lifespan into create_app() itself
(Redis client construction is synchronous/lazy) so both the WS and
REST-only paths always have them.

New tests/test_bots.py, test_message_edit.py, test_webhooks.py (full suite
now 78/78, stable across repeated runs) plus a scripted end-to-end smoke
test (bot WS join/post/edit, incoming webhook, SSRF rejection, outgoing
delivery) and a full browser walkthrough of the new admin/room UI.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/components/MessageList.css

@@ -42,6 +42,7 @@
 }
 
 .message-bubble {
+  position: relative;
   background: var(--ds-surface-2);
   color: var(--ds-text);
   padding: 8px 12px;
@@ -56,9 +57,45 @@
   background: var(--ds-accent-2);
 }
 
+.message-edit-link {
+  display: none;
+  position: absolute;
+  top: -18px;
+  right: 0;
+  background: transparent;
+  border: none;
+  color: var(--ds-muted);
+  font-size: 0.68rem;
+  cursor: pointer;
+  padding: 2px 4px;
+}
+
+.message-edit-link:hover {
+  color: var(--ds-text);
+}
+
+.message-bubble:hover .message-edit-link {
+  display: inline;
+}
+
+.message-edit-input {
+  background: var(--ds-surface-2);
+  border: 1px solid var(--ds-accent);
+  border-radius: 10px;
+  padding: 8px 12px;
+  font-size: 0.88rem;
+  color: var(--ds-text);
+  font-family: var(--sans);
+  width: 100%;
+}
+
 .message-time {
   font-size: 0.68rem;
   color: var(--ds-muted);
   margin-top: 3px;
   font-family: var(--mono);
 }
+
+.message-edited {
+  font-style: italic;
+}