feat(doctor): add duplicate filename conflict detection and one-click resolution

Detects when multiple model files share the same basename (causing
ambiguity in LoRA resolution), logs warnings during scanning, and
provides a "Resolve Conflicts" button in the Doctor panel. Resolution
renames duplicates with hash-prefixed unique filenames, migrates all
sidecar and preview files, and updates the cache and frontend scroller
in-place so the model modal immediately reflects the new filename.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

py/services/model_hash_index.py

@@ -79,6 +79,12 @@ class ModelHashIndex:
                     hash_val = h
                     break
         
+        if hash_val is None:
+            for h, paths in self._duplicate_hashes.items():
+                if file_path in paths:
+                    hash_val = h
+                    break
+        
         # If we didn't find a hash, nothing to do
         if not hash_val:
             return