Centralize MIME type initialization into utils/mime_types.py

Move mimetypes.init() and all custom type registrations from server.py
and metadata_extract.py into a single init_mime_types() function called
once at startup in main.py.

Amp-Thread-ID: https://ampcode.com/threads/T-019cbb2a-513a-7458-9962-b4100e4f124d
Co-authored-by: Amp <amp@ampcode.com>

utils/mime_types.py

@@ -0,0 +1,37 @@
+"""Centralized MIME type initialization.
+
+Call init_mime_types() once at startup to initialize the MIME type database
+and register all custom types used across ComfyUI.
+"""
+
+import mimetypes
+
+_initialized = False
+
+
+def init_mime_types():
+    """Initialize the MIME type database and register all custom types.
+
+    Safe to call multiple times; only runs once.
+    """
+    global _initialized
+    if _initialized:
+        return
+    _initialized = True
+
+    mimetypes.init()
+
+    # Web types (used by server.py for static file serving)
+    mimetypes.add_type('application/javascript; charset=utf-8', '.js')
+    mimetypes.add_type('image/webp', '.webp')
+
+    # Model and data file types (used by asset scanning / metadata extraction)
+    mimetypes.add_type("application/safetensors", ".safetensors")
+    mimetypes.add_type("application/safetensors", ".sft")
+    mimetypes.add_type("application/pytorch", ".pt")
+    mimetypes.add_type("application/pytorch", ".pth")
+    mimetypes.add_type("application/pickle", ".ckpt")
+    mimetypes.add_type("application/pickle", ".pkl")
+    mimetypes.add_type("application/gguf", ".gguf")
+    mimetypes.add_type("application/yaml", ".yaml")
+    mimetypes.add_type("application/yaml", ".yml")