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>

src/application/dtos/file_dto.rs

@@ -44,6 +44,10 @@ pub struct FileDto {
 
     /// Human-readable formatted size (e.g. "3.27 MB")
     pub size_formatted: String,
+
+    /// Owner user ID (omitted from JSON when None)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub owner_id: Option<String>,
 }
 
 impl From<File> for FileDto {
@@ -65,6 +69,7 @@ impl From<File> for FileDto {
             icon_special_class: icon_special_class_for(name, mime).to_string(),
             category: category_for(name, mime).to_string(),
             size_formatted: format_file_size(size),
+            owner_id: file.owner_id().map(String::from),
         }
     }
 }
@@ -103,6 +108,7 @@ impl FileDto {
             icon_special_class: String::new(),
             category: "Document".to_string(),
             size_formatted: "0 Bytes".to_string(),
+            owner_id: None,
         }
     }
 }