fix(fts): fix multi-word field-restricted search query building

Fixes a critical bug in FTS query building where multi-word searches
with field restrictions incorrectly used OR between all word+field
combinations instead of requiring ALL words to match within at least
one field.

Example: searching "cute cat" in {title, tags} previously produced:
  title:cute* OR title:cat* OR tags:cute* OR tags:cat*
Which matched recipes with ANY word in ANY field.

Now produces:
  (title:cute* title:cat*) OR (tags:cute* tags:cat*)
Which requires ALL words to match within at least one field.

Also adds fallback to fuzzy search when FTS returns empty results,
improving search reliability.

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

py/services/recipe_fts_index.py

@@ -509,21 +509,20 @@ class RecipeFTSIndex:
         if not fields:
             return term_expr
 
-        # Build field-restricted query with OR between fields
+        # Build field-restricted query where ALL words must match within at least one field
         field_clauses = []
         for field in fields:
             if field in self.FIELD_MAP:
                 cols = self.FIELD_MAP[field]
                 for col in cols:
-                    # FTS5 column filter syntax: column:term
-                    # Need to handle multiple terms properly
-                    for term in prefix_terms:
-                        field_clauses.append(f'{col}:{term}')
+                    # Create clause where ALL terms must match in this column (implicit AND)
+                    col_terms = [f'{col}:{term}' for term in prefix_terms]
+                    field_clauses.append('(' + ' '.join(col_terms) + ')')
 
         if not field_clauses:
             return term_expr
 
-        # Combine field clauses with OR
+        # Any field matching all terms is acceptable (OR between field clauses)
         return ' OR '.join(field_clauses)
 
     def _escape_fts_query(self, text: str) -> str:

py/services/recipe_scanner.py

@@ -632,7 +632,12 @@ class RecipeScanner:
             fields = None
 
         try:
-            return self._fts_index.search(search, fields)
+            result = self._fts_index.search(search, fields)
+            # Return None if empty to trigger fuzzy fallback
+            # Empty FTS results may indicate query syntax issues or need for fuzzy matching
+            if not result:
+                return None
+            return result
         except Exception as exc:
             logger.debug("FTS search failed, falling back to fuzzy search: %s", exc)
             return None

tests/services/test_recipe_fts_index.py

@@ -274,6 +274,81 @@ class TestRecipeFTSIndexFieldRestriction:
         results = fts_index.search('sunset', fields={'title', 'tags'})
         assert 'recipe-1' in results
 
+    def test_search_multiple_words_field_restricted(self, fts_index):
+        """Test that multi-word searches require ALL words to match within at least one field.
+
+        This is a regression test for the bug where field-restricted multi-word searches
+        incorrectly used OR between all word+field combinations, returning recipes that
+        only matched some of the search words.
+        """
+        # Create recipes that test multi-word matching:
+        # - recipe-1: both "cute" and "cat" in title
+        # - recipe-2: only "cute" in title
+        # - recipe-3: both words split across title and tags (should NOT match when searching title only)
+        # - recipe-4: both "cute" and "cat" in tags
+        # - recipe-5: only "cat" in title
+        test_recipes = [
+            {
+                'id': 'recipe-1',
+                'title': 'cute cat photo',
+                'tags': ['animal'],
+                'loras': [],
+                'gen_params': {},
+            },
+            {
+                'id': 'recipe-2',
+                'title': 'cute dog picture',
+                'tags': ['pet'],
+                'loras': [],
+                'gen_params': {},
+            },
+            {
+                'id': 'recipe-3',
+                'title': 'cute',
+                'tags': ['cat', 'animal'],  # "cute" in title, "cat" in tags
+                'loras': [],
+                'gen_params': {},
+            },
+            {
+                'id': 'recipe-4',
+                'title': 'kitten image',
+                'tags': ['cute', 'cat'],  # both words in tags
+                'loras': [],
+                'gen_params': {},
+            },
+            {
+                'id': 'recipe-5',
+                'title': 'cat only',
+                'tags': [],
+                'loras': [],
+                'gen_params': {},
+            },
+        ]
+        fts_index.build_index(test_recipes)
+
+        # Search "cute cat" in title only - should only match recipe-1 (both words in title)
+        results = fts_index.search('cute cat', fields={'title'})
+        assert results == {'recipe-1'}, f"Expected only recipe-1, got {results}"
+
+        # Search "cute cat" in tags only - should only match recipe-4 (both words in tags)
+        results = fts_index.search('cute cat', fields={'tags'})
+        assert results == {'recipe-4'}, f"Expected only recipe-4, got {results}"
+
+        # Search "cute cat" in both title and tags - should match recipe-1 and recipe-4
+        # (each has both words in one of the specified fields)
+        results = fts_index.search('cute cat', fields={'title', 'tags'})
+        assert results == {'recipe-1', 'recipe-4'}, f"Expected recipe-1 and recipe-4, got {results}"
+
+        # Search without field restriction - should match recipes where words appear in any indexed field
+        results = fts_index.search('cute cat')
+        # recipe-1, recipe-2 (cute), recipe-3 (cute in title, cat in tags), recipe-4, recipe-5 (cat)
+        # Actually, without field restriction, FTS searches all fields as one bag of content
+        # So any recipe with both "cute" and "cat" anywhere should match
+        assert 'recipe-1' in results  # both in title
+        assert 'recipe-4' in results  # both in tags
+        # recipe-3: "cute" in title, "cat" in tags - both words present
+        assert 'recipe-3' in results
+
 
 class TestRecipeFTSIndexIncrementalOperations:
     """Tests for incremental add/remove/update operations."""