feat: implement update management web UI

Add complete update management interface to web UI:
- Update status display (current version, last status, timestamp, errors)
- Check for updates button with availability indicator
- Apply update button with confirmation dialog and backup warnings
- Rollback button with confirmation dialog
- Update logs viewer (collapsible, reverse chronological)
- Auto-refresh after update/rollback actions (5s delay)

Features:
- Uses existing Pico CSS framework for consistent styling
- Integrates with existing auth system (Bearer token/session cookies)
- Real-time feedback with loading states and error handling
- German UI language matching existing interface
- All API calls use existing api() helper function

Complete US_000029-033 and TASK_000030-034:
- US_000029: Display update status in web UI
- US_000030: Trigger update check from UI
- US_000031: Apply updates from UI
- US_000032: Display update logs in UI
- US_000033: Trigger rollback from UI

EPIC_000008 (Client-Side Update Mechanism) now fully complete.
Documentation updated per SOP (CHANGELOG, PROJECT_STATUS, stories/tasks).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

project-management/PROJECT_STATUS.md

@@ -92,16 +92,16 @@ Sicheres, remote steuerbares System zum Sperren/Entsperren lokaler Nutzerkonten.
 - [x] TASK_000028: Verify and apply update
 - [x] US_000028: Client meldet Update-Status
 - [x] TASK_000029: Report update status
-- [ ] US_000029: Update-Status im Web-UI anzeigen
-- [ ] TASK_000030: UI update status view
-- [ ] US_000030: Update-Check im Web-UI ausloesen
-- [ ] TASK_000031: UI update check trigger
-- [ ] US_000031: Update im Web-UI anstossen
-- [ ] TASK_000032: UI update apply action
-- [ ] US_000032: Update-Logs im Web-UI anzeigen
-- [ ] TASK_000033: UI update logs view
-- [ ] US_000033: Rollback im Web-UI anstossen
-- [ ] TASK_000034: UI rollback action
+- [x] US_000029: Update-Status im Web-UI anzeigen
+- [x] TASK_000030: UI update status view
+- [x] US_000030: Update-Check im Web-UI ausloesen
+- [x] TASK_000031: UI update check trigger
+- [x] US_000031: Update im Web-UI anstossen
+- [x] TASK_000032: UI update apply action
+- [x] US_000032: Update-Logs im Web-UI anzeigen
+- [x] TASK_000033: UI update logs view
+- [x] US_000033: Rollback im Web-UI anstossen
+- [x] TASK_000034: UI rollback action
 
 ### EPIC_000009: Update Webservice (External Team)
 - [ ] US_000026: Client bezieht Updates (Pull)