Add timeout protection to cache generation

Prevents backend from hanging when parsing problematic pattern files.
Files that take longer than 30 seconds to parse are skipped with an error log.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

modules/core/cache_manager.py

@@ -448,20 +448,26 @@ async def generate_image_preview(pattern_file):
             # Parse file to get metadata (this is the only time we need to parse)
             logger.debug(f"Parsing {pattern_file} for metadata cache")
             pattern_path = os.path.join(THETA_RHO_DIR, pattern_file)
-            
+
             try:
-                coordinates = await asyncio.to_thread(parse_theta_rho_file, pattern_path)
-                
+                # Add timeout protection to prevent hanging on problematic files
+                coordinates = await asyncio.wait_for(
+                    asyncio.to_thread(parse_theta_rho_file, pattern_path),
+                    timeout=30.0  # 30 second timeout per file
+                )
+
                 if coordinates:
                     first_coord = {"x": coordinates[0][0], "y": coordinates[0][1]}
                     last_coord = {"x": coordinates[-1][0], "y": coordinates[-1][1]}
                     total_coords = len(coordinates)
-                    
+
                     # Cache the metadata for future use
                     cache_pattern_metadata(pattern_file, first_coord, last_coord, total_coords)
                     logger.debug(f"Metadata cached for {pattern_file}: {total_coords} coordinates")
                 else:
                     logger.warning(f"No coordinates found in {pattern_file}")
+            except asyncio.TimeoutError:
+                logger.error(f"Timeout parsing {pattern_file} for metadata - skipping")
             except Exception as e:
                 logger.error(f"Failed to parse {pattern_file} for metadata: {str(e)}")
                 # Continue with image generation even if metadata fails
@@ -620,21 +626,29 @@ async def generate_metadata_cache():
                 cache_progress["current_file"] = file_name
                 
                 try:
-                    # Parse file to get metadata
-                    coordinates = await asyncio.to_thread(parse_theta_rho_file, pattern_path)
+                    # Parse file to get metadata with timeout protection
+                    try:
+                        coordinates = await asyncio.wait_for(
+                            asyncio.to_thread(parse_theta_rho_file, pattern_path),
+                            timeout=30.0  # 30 second timeout per file
+                        )
+                    except asyncio.TimeoutError:
+                        logger.error(f"Timeout parsing {file_name} - skipping (file may be too large or corrupted)")
+                        continue
+
                     if coordinates:
                         first_coord = {"x": coordinates[0][0], "y": coordinates[0][1]}
                         last_coord = {"x": coordinates[-1][0], "y": coordinates[-1][1]}
                         total_coords = len(coordinates)
-                        
+
                         # Cache the metadata
                         cache_pattern_metadata(file_name, first_coord, last_coord, total_coords)
                         successful += 1
                         logger.debug(f"Generated metadata for {file_name}")
-                        
+
                     # Small delay to reduce I/O pressure
                     await asyncio.sleep(0.05)
-                    
+
                 except Exception as e:
                     logger.error(f"Failed to generate metadata for {file_name}: {str(e)}")