refactor(main): search_tags JOINs fandom; matches on display CONCAT

Post-refactor tag.name is bare. Autocomplete needs to match the
display form (name + ' (' + fandom.name + ')') so users can still
find 'Ruby Rose (RWBY)' by typing 'rwby'. Switched to
contains_eager(Tag.fandom, alias=f) to eliminate the duplicate
join that caused a Postgres GROUP BY error in the no-query path.

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

app/main.py

@@ -3,7 +3,7 @@
 from flask import Blueprint, render_template, flash, redirect, url_for, abort, send_from_directory, request, jsonify, current_app
 
 from sqlalchemy import desc, func, text, extract, and_
-from sqlalchemy.orm import joinedload, aliased
+from sqlalchemy.orm import joinedload, aliased, contains_eager
 from collections import OrderedDict
 from datetime import datetime
 
@@ -637,28 +637,41 @@ def search_tags():
     """
     Search existing tags for autocomplete.
     Query params:
-      - q: search query (matches tag name, case-insensitive)
+      - q: search query (matches against display_name, case-insensitive)
       - limit: max results (default 10)
-      - exclude_kind: comma-separated list of tag kinds to exclude (e.g., 'archive')
+      - exclude_kind: comma-separated list of tag kinds to exclude
-      - kind: filter to only include tags of this kind (e.g., 'series')
+      - kind: filter to only include tags of this kind
     """
-    query = request.args.get('q', '').strip().lower()
+    from sqlalchemy import case
-    limit = request.args.get('limit', 10, type=int)
+
-    exclude_kind = request.args.get('exclude_kind', '').strip()
+    query = request.args.get("q", "").strip().lower()
-    exclude_kinds = [k.strip() for k in exclude_kind.split(',') if k.strip()]
+    limit = request.args.get("limit", 10, type=int)
-    include_kind = request.args.get('kind', '').strip()
+    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()
+
+    f = aliased(Tag)
+    display_expr = case(
+        (
+            and_(Tag.kind == "character", Tag.fandom_id.isnot(None)),
+            func.concat(Tag.name, " (", f.name, ")"),
+        ),
+        else_=Tag.name,
+    )
+
+    base_query = (
+        db.session.query(Tag)
+        .outerjoin(f, f.id == Tag.fandom_id)
+        .options(contains_eager(Tag.fandom, alias=f))
+    )
+    if exclude_kinds:
+        base_query = base_query.filter(~Tag.kind.in_(exclude_kinds))
+    if include_kind:
+        base_query = base_query.filter(Tag.kind == include_kind)
 
     if not query:
-        # Return most-used tags when no query
+        # No query: most-used tags.
-        base_query = (
+        base_query = base_query.join(image_tags, image_tags.c.tag_id == Tag.id).group_by(Tag.id, f.id)
-            Tag.query
-            .join(image_tags)
-            .group_by(Tag.id)
-        )
-        if exclude_kinds:
-            base_query = base_query.filter(~Tag.kind.in_(exclude_kinds))
-        if include_kind:
-            base_query = base_query.filter(Tag.kind == include_kind)
         tags = (
             base_query
             .order_by(func.count(image_tags.c.image_id).desc())
@@ -666,14 +679,10 @@ def search_tags():
             .all()
         )
     else:
-        base_query = Tag.query.filter(Tag.name.ilike(f'%{query}%'))
+        base_query = base_query.filter(display_expr.ilike(f"%{query}%"))
-        if exclude_kinds:
-            base_query = base_query.filter(~Tag.kind.in_(exclude_kinds))
-        if include_kind:
-            base_query = base_query.filter(Tag.kind == include_kind)
         tags = (
             base_query
-            .order_by(Tag.name)
+            .order_by(display_expr)
             .limit(limit)
             .all()
         )
@@ -682,9 +691,10 @@ def search_tags():
         {
             "id": t.id,
             "name": t.name,
+            "display_name": t.display_name,
             "kind": t.kind,
             "fandom_id": t.fandom_id if t.kind == "character" else None,
-            "fandom_name": (t.fandom.name.split(":", 1)[1] if t.fandom else None) if t.kind == "character" else None
+            "fandom_name": (t.fandom.name if t.fandom else None) if t.kind == "character" else None,
         }
         for t in tags
     ])