feat(nextcloud): add Nextcloud-compatible API layer

Implement a complete Nextcloud client compatibility layer so that
Nextcloud desktop/mobile sync clients can connect to OxiCloud.

Key additions:
- Login Flow v2 (device auth) with OIDC bridge support
- WebDAV handler compatible with Nextcloud clients (PROPFIND, GET,
  PUT, DELETE, MKCOL, MOVE, COPY, HEAD, PROPPATCH)
- OCS API endpoints (user info, capabilities, notifications stubs,
  sharees, unified search)
- Basic Auth middleware with app password verification, account
  lockout integration, and blake3-keyed auth cache
- App password management: create, list, revoke via both native
  API (JWT-authenticated profile page) and Nextcloud OCS endpoints
- Nextcloud file ID mapping (oc:fileid) with persistent DB storage
- Chunked upload support (Nextcloud v2 chunking protocol)
- Trashbin WebDAV interface
- Avatar (SVG placeholder) and preview (redirect) handlers
- User profile page with app password management UI
- URL user validation on all DAV routes (403 on mismatch)
- Database schema for app_passwords and nextcloud_object_ids tables

All services are behind a `nextcloud.enabled` config flag and
cleanly separated under src/interfaces/nextcloud/.

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

src/common/stubs.rs

@@ -96,6 +96,10 @@ impl FileReadPort for StubFileReadPort {
         Ok("root".to_string())
     }
 
+    async fn get_folder_id_by_path(&self, _folder_path: &str) -> Result<String, DomainError> {
+        Ok("stub-folder-id".to_string())
+    }
+
     async fn get_blob_hash(&self, _file_id: &str) -> Result<String, DomainError> {
         Ok(String::new())
     }
@@ -773,6 +777,10 @@ impl DedupPort for StubDedupPort {
         Ok(String::new())
     }
 
+    fn blob_path(&self, hash: &str) -> PathBuf {
+        PathBuf::from(format!("stub_blob_{}.blob", hash))
+    }
+
     async fn get_stats(&self) -> DedupStatsDto {
         DedupStatsDto::default()
     }