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>

docker-compose.wopi.yml

@@ -0,0 +1,31 @@
+# WOPI editor services for local development.
+# Usage: docker compose -f docker-compose.dev.yml -f docker-compose.wopi.yml up -d
+# Then run OxiCloud natively: cargo run
+
+services:
+  collabora:
+    image: collabora/code:latest
+    restart: unless-stopped
+    cap_add:
+      - MKNOD
+    environment:
+      # Allow OxiCloud running on host to use Collabora
+      - "aliasgroup1=http://host.docker.internal:8086"
+      # Disable SSL and SSL termination (dev only, plain HTTP on localhost)
+      - "extra_params=--o:ssl.enable=false --o:ssl.termination=false --o:net.frame_ancestors=http://localhost:* http://127.0.0.1:*"
+      # Admin console (optional)
+      - "username=admin"
+      - "password=admin"
+    ports:
+      - "9980:9980"
+
+  # Uncomment to use OnlyOffice instead of / alongside Collabora:
+  # onlyoffice:
+  #   image: onlyoffice/documentserver:latest
+  #   restart: unless-stopped
+  #   environment:
+  #     - "WOPI_ENABLED=true"
+  #     - "JWT_SECRET=oxicloud-dev-secret"
+  #     - "JWT_ENABLED=true"
+  #   ports:
+  #     - "8088:80"