fix(autocomplete): parse kind:rest in /api/tags/search

The add-tag input lets the user type 'character:mocha' as a kind shortcut,
but the autocomplete was passing the whole query through to ilike, so
'%character:mocha%' never matched any display_name. Use parse_kind_prefix
to split the prefix into a kind filter, leaving the rest as the search
term. An explicit ?kind= (e.g. fandom picker) still wins. Empty rest
('character:') falls into the no-query branch and shows top characters.

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

app/main.py

@@ -663,13 +663,26 @@ def search_tags():
       - kind: filter to only include tags of this kind
     """
     from sqlalchemy import case
+    from app.utils.tag_prefix import parse_kind_prefix
 
-    query = request.args.get("q", "").strip().lower()
+    raw_q = request.args.get("q", "").strip()
     limit = request.args.get("limit", 10, type=int)
     exclude_kind = request.args.get("exclude_kind", "").strip()
     exclude_kinds = [k.strip() for k in exclude_kind.split(",") if k.strip()]
     include_kind = request.args.get("kind", "").strip()
 
+    # Honour the same `kind:rest` shortcut the add-tag input uses, so typing
+    # "character:mocha" filters to character rows matching "mocha" instead of
+    # ilike-matching the literal "character:" string against display_name.
+    # An explicit ?kind= still wins (used by the fandom picker).
+    if not include_kind:
+        parsed_kind, parsed_rest = parse_kind_prefix(raw_q)
+        if parsed_kind is not None:
+            include_kind = parsed_kind
+            raw_q = parsed_rest
+
+    query = raw_q.lower()
+
     f = aliased(Tag)
     display_expr = case(
         (