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/infrastructure/services/dedup_service.rs

@@ -110,6 +110,23 @@ impl DedupService {
         }
     }
 
+    /// Creates a stub instance for testing — never hits PG or the filesystem.
+    #[cfg(test)]
+    pub fn new_stub() -> Self {
+        let stub_pool = Arc::new(
+            sqlx::pool::PoolOptions::<sqlx::Postgres>::new()
+                .max_connections(1)
+                .connect_lazy("postgres://invalid:5432/none")
+                .unwrap(),
+        );
+        Self {
+            blob_root: std::path::PathBuf::from("/tmp/oxicloud_stub_blobs"),
+            temp_root: std::path::PathBuf::from("/tmp/oxicloud_stub_temp"),
+            pool: stub_pool.clone(),
+            maintenance_pool: stub_pool,
+        }
+    }
+
     /// Initialize the service (create blob directories on the filesystem).
     pub async fn initialize(&self) -> Result<(), DomainError> {
         // Create directories
@@ -903,6 +920,10 @@ impl DedupPort for DedupService {
             .map_err(DomainError::from)
     }
 
+    fn blob_path(&self, hash: &str) -> PathBuf {
+        self.blob_path(hash)
+    }
+
     async fn get_stats(&self) -> DedupStatsDto {
         self.get_stats().await
     }