fix(thumbnail): add timeout protection for large image processing

Resolves conflict between main and PR #229 by applying timeout support
on top of main's drop(data) memory optimization. Changes:
- Add thumbnail_generation_ms to TimeoutConfig (default 30s)
- Add generation_timeout field to ThumbnailService
- Wrap spawn_blocking in tokio::time::timeout to prevent hanging
- Update DI to pass timeout from config
- Update tests to provide timeout parameter

https://claude.ai/code/session_015FD62aAoMYx1XBZbzPvUu8

src/common/config.rs

@@ -34,15 +34,18 @@ pub struct TimeoutConfig {
     pub lock_acquisition_ms: u64,
     /// Timeout for network operations (ms)
     pub network_operation_ms: u64,
+    /// Timeout for thumbnail generation (ms)
+    pub thumbnail_generation_ms: u64,
 }
 
 impl Default for TimeoutConfig {
     fn default() -> Self {
         Self {
-            file_operation_ms: 10000,    // 10 seconds
-            dir_operation_ms: 30000,     // 30 seconds
-            lock_acquisition_ms: 5000,   // 5 seconds
-            network_operation_ms: 15000, // 15 seconds
+            file_operation_ms: 10000,       // 10 seconds
+            dir_operation_ms: 30000,        // 30 seconds
+            lock_acquisition_ms: 5000,      // 5 seconds
+            network_operation_ms: 15000,    // 15 seconds
+            thumbnail_generation_ms: 30000, // 30 seconds
         }
     }
 }
@@ -82,6 +85,11 @@ impl TimeoutConfig {
     pub fn network_timeout(&self) -> Duration {
         Duration::from_millis(self.network_operation_ms)
     }
+
+    /// Gets a Duration for thumbnail generation operations
+    pub fn thumbnail_timeout(&self) -> Duration {
+        Duration::from_millis(self.thumbnail_generation_ms)
+    }
 }
 
 /// Configuration for large resource handling