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/application/ports/storage_ports.rs

@@ -82,6 +82,9 @@ pub trait FileReadPort: Send + Sync + 'static {
     /// Gets the parent folder ID from a path (WebDAV).
     async fn get_parent_folder_id(&self, path: &str) -> Result<String, DomainError>;
 
+    /// Gets a folder ID by its path.
+    async fn get_folder_id_by_path(&self, folder_path: &str) -> Result<String, DomainError>;
+
     /// Gets the content-addressable blob hash for a file (O(1) DB lookup).
     ///
     /// Returns the BLAKE3 hash stored in `storage.files.blob_hash`.