feat(wopi): add WOPI protocol support for collaborative editing

Implement the Web Application Open Platform Interface (WOPI) protocol
to enable collaborative document editing with Collabora Online and
OnlyOffice through OxiCloud.

Backend:
- WOPI token service with HMAC-SHA256 signed access tokens
- WOPI lock service with in-memory lock management and expiry
- WOPI discovery service for auto-detecting editor capabilities
- WOPI HTTP handler: CheckFileInfo, GetFile, PutFile, Lock/Unlock
- File entity extended with owner_id for WOPI file-info responses
- Configuration via WOPI_* environment variables
- Services wired through DI in AppState

Frontend:
- WOPI editor component with modal and new-tab viewing modes
- Context menu integration for opening files in online editors
- Inline viewer integration for document preview

Infrastructure:
- Docker Compose file for local Collabora/OnlyOffice dev setup

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

static/index.html

@@ -34,6 +34,7 @@
     <script defer src="/js/features/sharing/fileSharing.js"></script>
     <script defer src="/js/views/shared/sharedView.js"></script>
     <script defer src="/js/features/files/inlineViewer.js"></script>
+    <script defer src="/js/features/files/wopiEditor.js"></script>
     <script defer src="/js/core/icons.js"></script>
     <script defer src="/js/app/navigation.js"></script>
     <script defer src="/js/app/authSession.js"></script>