fix(db): apply sqlc's actual output for candidate_artist_tags — #2376

Three divergences in the hand-written generated file, all caught by
verify-generate on the first run. Two are sqlc rules I had wrong:

1. When a query's SELECT list exactly matches a table's columns in order,
   sqlc REUSES the model struct rather than emitting a bespoke Row type.
   So ListCandidateArtistTagsForMbids returns []CandidateArtistTag, and
   ListCandidateArtistTagsForMbidsRow should never have existed.

2. models.go is ordered by GO STRUCT NAME, not table name. Table order
   would put candidate_artist_tag_state before candidate_artist_tags;
   sqlc emits CandidateArtistTag before CandidateArtistTagState. The
   earlier slice-3 observation ("ordered by table name") was consistent
   with both orderings and so never discriminated — this case does.

3. sqlc smart-quotes a doubled '' inside a promoted comment into a
   typographic ”. Reworded the prose to say "the empty string" instead of
   encoding a mangling into the source.

Note the integration lane PASSED on the broken push while this failed.
That is #2380's lesson landing again, and the reason the check exists:
valid SQL executing against real Postgres proves nothing about whether
the committed Go matches its source.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

internal/db/dbq/models.go

@@ -240,6 +240,12 @@ type AuditLog struct {
 	CreatedAt pgtype.Timestamptz
 }
 
+type CandidateArtistTag struct {
+	CandidateMbid string
+	Tag           string
+	Weight        float64
+}
+
 type CandidateArtistTagState struct {
 	CandidateMbid     string
 	TagSource         string
@@ -247,12 +253,6 @@ type CandidateArtistTagState struct {
 	UpdatedAt         pgtype.Timestamptz
 }
 
-type CandidateArtistTag struct {
-	CandidateMbid string
-	Tag           string
-	Weight        float64
-}
-
 type ContextualLike struct {
 	ID            pgtype.UUID
 	UserID        pgtype.UUID