Bump to v1.1.0 and bring all documentation current

Version bump in both pyproject.toml and package.json. Documentation
update covers everything shipped since v1.0.0 (direct messages,
message deletion, custom emoji, video attachments, DM/room email
notifications, active sessions, and more), and corrects claims that
had gone stale -- backend/README.md and DEPLOYMENT.md both still said
"no server-side session revocation" and backend/README.md said "no
custom/uploaded emoji," both now false.

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

backend/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "ds-chat"
-version = "1.0.0"
+version = "1.1.0"
 description = "DS Chat backend service"
 license = { text = "AGPL-3.0-or-later" }
 requires-python = ">=3.11"