feat(search): viewer progress + completed badges; dropdown to templ

Search results now show where you are in a book: a completed check at
the 0.999 threshold (same cut as the filter status arms), a partial
progress bar along the cover while mid-read, nothing when you never
opened it. Rendered in BookCard (any grid whose adapter loads viewer
progress) and in the header-search dropdown rows.

The progress rides a LEFT JOIN reading_progress on the SAME user_id
param SearchMediaItemsUnified already binds for library visibility —
one requester param, no new wire inputs, row-neutral join (the table
is UNIQUE per media_item+user). SearchMediaItemsUnifiedRow and BookInfo
gain the keys additively (viewer_percentage null when unknown,
library_name empty on feeds that don't load it); contract_pins.md
carries the changelog entry and the pin tests widen in lockstep.

The header dropdown itself migrates off the innerHTML string renderer
in search.ts (a rendering-ownership violation: a templ twin existed via
the HX-Request branch). The input now hx-gets layout=dropdown and swaps
the new templ SearchResults partial — titles/authors highlighted
server-side (escape-first, safe by construction), rows with the same
progress overlays — while a slim Alpine component owns only
client-local state (min-length gating, open/close, keyboard selection,
htmx lifecycle). web/src/rendering-allowlist.txt drops the search.ts
baseline to zero accordingly.

Integration test pins the per-user join (fresh user sees 1.0/0.42/null
on the fixture; the shared admin sees null everywhere — read-only) and
the dropdown partial's overlays/count/row count.

internal/database/querier.go

@@ -275,12 +275,24 @@ type Querier interface {
 	// Series are grouped PER LIBRARY: the same series name in two libraries
 	// (novels vs manga adaptations, LN splits) stays two entries. Visible
 	// filter enforces per-user library visibility at the source.
-	// Tiebreaker REQUIRED for LIMIT/OFFSET pagination: bulk imports in one
-	// transaction share a single NOW() timestamp, leaving many groups tied on
-	// MAX(created_at). Postgres does not guarantee tie order between
-	// executions, so page boundaries could repeat or drop series. The GROUP BY
-	// keys make the sort total and deterministic.
+	//
+	// Series-page sort/filter contract (extensible registry in
+	// services.ResolveSeriesSort): SeriesQuery is a series-NAME substring so
+	// it filters in WHERE (the group key — counts stay true); AuthorQuery
+	// and Status filter via HAVING so COUNT(*) keeps reporting the whole
+	// series. ViewerUserId scopes the per-user progress aggregates (the rp
+	// join can't multiply rows: reading_progress is UNIQUE per
+	// media_item+user). Sort is a BOUND PARAM compared inside the CASE
+	// cascade — never interpolated — and the GROUP BY tiebreaker stays
+	// REQUIRED for LIMIT/OFFSET determinism: bulk imports in one
+	// transaction share a single NOW() timestamp, leaving many groups tied
+	// on MAX(created_at), and Postgres does not guarantee tie order between
+	// executions, so page boundaries could repeat or drop series.
 	GetDistinctSeries(ctx context.Context, arg GetDistinctSeriesParams) ([]GetDistinctSeriesRow, error)
+	// Count counterpart of GetDistinctSeries: identical WHERE + JOIN +
+	// HAVING so the pagination total matches what the page query returns
+	// under the same filters (Sort is a page-ORDER concern, not a set
+	// membership one, so it is absent here by design).
 	GetDistinctSeriesCount(ctx context.Context, arg GetDistinctSeriesCountParams) (int32, error)
 	GetFailedSyncQueueItems(ctx context.Context, limit int32) ([]SyncQueue, error)
 	GetFirstAdmin(ctx context.Context) (pgtype.UUID, error)