feat: remove ai-chat extension from hosted version, move chat widget to bottom-right

Remove ai-chat from extensions.config.json and docker/extensions.hosted.json
(kept in self-hosted config). Remove ChatWidget imports from dashboard layout
and root page. Reposition chat widget FAB and panel to bottom-right corner.
Regenerate extension registry.

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

lib/extensions/_generated/enabled-extensions.ts

@@ -2,6 +2,5 @@
 
 export const ENABLED_EXTENSION_IDS: ReadonlySet<string> = new Set([
   'enable-banking',
-  'ai-chat',
   'email',
 ])