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/common/config.rs

@@ -200,6 +200,9 @@ pub struct StorageConfig {
     pub parallel_threshold: usize,
     /// Retention days for files in the trash
     pub trash_retention_days: u32,
+    /// Maximum upload file size in bytes (default: 10 GB).
+    /// Applied as a hard limit to WebDAV PUT and streaming uploads.
+    pub max_upload_size: usize,
 }
 
 impl Default for StorageConfig {
@@ -209,6 +212,7 @@ impl Default for StorageConfig {
             chunk_size: 1024 * 1024,               // 1 MB
             parallel_threshold: 100 * 1024 * 1024, // 100 MB
             trash_retention_days: 30,              // 30 days
+            max_upload_size: 10 * 1024 * 1024 * 1024, // 10 GB
         }
     }
 }
@@ -566,6 +570,14 @@ impl AppConfig {
             config.features.enable_search = val;
         }
 
+        // Storage limits
+        if let Ok(max_upload) = env::var("OXICLOUD_MAX_UPLOAD_SIZE")
+            .map(|v| v.parse::<usize>())
+            && let Ok(val) = max_upload
+        {
+            config.storage.max_upload_size = val;
+        }
+
         // OIDC configuration
         if let Ok(v) = env::var("OXICLOUD_OIDC_ENABLED") {
             config.oidc.enabled = v.parse::<bool>().unwrap_or(false);