fix search/filter bugs in game and TV libraries

- Game series: filter now checks child games for both search and tag matches instead of always passing series through
- TV episodes: tag selector no longer closes after picking a tag
- TV episodes: filter panel now filters episodes within a season view
- TV series list: series now appear when any of their episodes match the active tag filter (via new /api/tv/series-episode-tags endpoint backed by media_items)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/api/tv/series-episode-tags/route.ts

@@ -0,0 +1,14 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { getSeriesEpisodeTagMap } from '@/lib/tags'
+import { requireLibraryAccess } from '@/lib/auth'
+
+export async function GET(request: NextRequest) {
+  const { searchParams } = request.nextUrl
+  const libraryId = searchParams.get('libraryId')
+  if (!libraryId) return NextResponse.json({ error: 'libraryId required' }, { status: 400 })
+
+  const auth = await requireLibraryAccess(request, libraryId)
+  if (auth instanceof NextResponse) return auth
+
+  return NextResponse.json(getSeriesEpisodeTagMap(libraryId))
+}