Fix Dockerfile: use external patch script instead of inline Python

Docker's parser chokes on multi-line Python in RUN. Moved to
scripts/patch_utils.py and COPY + RUN it.

scripts/patch_utils.py

@@ -0,0 +1,23 @@
+"""Patch vLLM's process_weights_after_loading to call model._post_quant_fix()
+after all quant methods have set up their attributes."""
+import sys
+
+path = sys.argv[1]
+with open(path) as f:
+    src = f.read()
+
+old = '    if model_config.quantization == "torchao":'
+new = '''    # Custom: allow models to run post-quant-init fixes
+    if hasattr(model, '_post_quant_fix'):
+        model._post_quant_fix()
+
+    if model_config.quantization == "torchao":'''
+
+if old not in src:
+    print(f"WARNING: Could not find patch target in {path}")
+    sys.exit(1)
+
+src = src.replace(old, new, 1)
+with open(path, 'w') as f:
+    f.write(src)
+print('Patched process_weights_after_loading')