fix: OOM protection, lock-free thumbnail cache, OIDC JWKS TTL

- Streaming WebDAV PUT: body spooled to tempfile with incremental SHA-256,
  peak RAM ~64KB regardless of file size (Solution 2)
- RequestBodyLimitLayer (1MB) on CalDAV/CardDAV routers (Solution 3)
- All body::to_bytes(body, usize::MAX) replaced with explicit limits:
  PROPFIND/PROPPATCH/LOCK → 1MB, MKCOL → 4KB
- Added AppError::payload_too_large (HTTP 413)
- Added max_upload_size to StorageConfig (default 10GB, env override)
- New streaming update chain: FileWritePort::update_file_content_from_temp
  → FileUploadUseCase::update_file_streaming
- ThumbnailService: migrated from RwLock<LruCache> to moka::future::Cache
  with weight-based eviction — eliminates lock contention on read hot-path
- OIDC: discovery + JWKS caches now expire after 1 hour (Cached<T> wrapper)
  so IdP key rotation no longer requires server restart

src/interfaces/errors.rs

@@ -95,6 +95,15 @@ impl AppError {
             "PreconditionFailed",
         )
     }
+
+    /// Create a 413 Payload Too Large error.
+    pub fn payload_too_large(message: impl Into<String>) -> Self {
+        Self::new(
+            StatusCode::PAYLOAD_TOO_LARGE,
+            message,
+            "PayloadTooLarge",
+        )
+    }
 }
 
 impl From<DomainError> for AppError {