feat: expose comfy-api/platform base URLs via /features

Adds --comfy-platform-base CLI flag mirroring --comfy-api-base, and
surfaces both through the existing /features endpoint as
comfy_api_base_url and comfy_platform_base_url. Lets the frontend
discover at runtime which backend the local server expects it to talk
to, so an ephemeral or self-hosted comfy-api deployment can be wired up
without rebuilding the frontend bundle.

Companion frontend change consumes these keys.

comfy/cli_args.py

@@ -231,6 +231,13 @@ parser.add_argument(
     help="Set the base URL for the ComfyUI API.  (default: https://api.comfy.org)",
 )
 
+parser.add_argument(
+    "--comfy-platform-base",
+    type=str,
+    default="https://platform.comfy.org",
+    help="Set the base URL for the ComfyUI Platform.  (default: https://platform.comfy.org)",
+)
+
 database_default_path = os.path.abspath(
     os.path.join(os.path.dirname(__file__), "..", "user", "comfyui.db")
 )

comfy_api/feature_flags.py

@@ -99,6 +99,8 @@ _CORE_FEATURE_FLAGS: dict[str, Any] = {
     "extension": {"manager": {"supports_v4": True}},
     "node_replacements": True,
     "assets": args.enable_assets,
+    "comfy_api_base_url": args.comfy_api_base,
+    "comfy_platform_base_url": args.comfy_platform_base,
 }
 
 # CLI-provided flags cannot overwrite core flags