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>

app/page.tsx

@@ -3,7 +3,6 @@ import { redirect } from 'next/navigation'
 import DashboardNav from '@/components/dashboard/DashboardNav'
 import DashboardContent from '@/components/dashboard/DashboardContent'
 import type { Deadline, ReceiptQueueSummary } from '@/types'
-import { ChatWidget } from '@/components/chat'
 
 export default async function RootPage() {
   const supabase = await createClient()
@@ -230,7 +229,6 @@ export default async function RootPage() {
             enabledExtensions={enabledToggles || []}
           />
         </div>
-        <ChatWidget />
       </main>
     </div>
   )