Unify media_key and item_key — use item_key everywhere

media_key was a lossy shortening of item_key (libraryId:lastSegment) that
introduced a real collision bug: two TV episodes from different series with
the same filename would share the same media_key and each other's tags.

- DB migration converts existing media_tags rows from short format to full
  item_key by joining against media_items; ambiguous/orphaned rows are dropped
- media_tags column renamed media_key → item_key
- Removed itemKeyToMediaKey() from scanner; reconcileAndPrune now passes
  item_key directly to reKeyMediaItem
- DB reader functions (tv, movies, games) now expose item_key on returned
  entities; frontend components use entity.item_key instead of constructing
  the short libraryId:id form
- MixedView now constructs the full mixed_file: item_key format
- Tag API renamed mediaKey param → itemKey throughout

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

src/app/api/movies/route.ts

@@ -64,7 +64,7 @@ export async function DELETE(request: NextRequest) {
     return NextResponse.json({ error: 'Failed to delete movie directory' }, { status: 500 })
   }
 
-  removeAllAssignmentsForItem(`${libraryId}:${movieId}`)
+  removeAllAssignmentsForItem(`${libraryId}:movie:${movieId}`)
 
   return new NextResponse(null, { status: 204 })
 }

src/app/api/tags/assignments/route.ts

@@ -2,27 +2,27 @@ import { NextRequest, NextResponse } from 'next/server'
 import { getResolvedTagsForItem, addTagToItem, removeTagFromItem } from '@/lib/tags'
 import { requireLibraryAccess } from '@/lib/auth'
 
-function extractLibraryId(mediaKey: string): string | null {
-  const colonIdx = mediaKey.indexOf(':')
+function extractLibraryId(itemKey: string): string | null {
+  const colonIdx = itemKey.indexOf(':')
   if (colonIdx === -1) return null
-  return mediaKey.slice(0, colonIdx)
+  return itemKey.slice(0, colonIdx)
 }
 
 export async function GET(request: NextRequest) {
   try {
     const { searchParams } = new URL(request.url)
-    const mediaKey = searchParams.get('mediaKey')
-    if (!mediaKey) {
-      return NextResponse.json({ error: 'mediaKey is required' }, { status: 400 })
+    const itemKey = searchParams.get('itemKey')
+    if (!itemKey) {
+      return NextResponse.json({ error: 'itemKey is required' }, { status: 400 })
     }
-    const libraryId = extractLibraryId(mediaKey)
+    const libraryId = extractLibraryId(itemKey)
     if (!libraryId) {
-      return NextResponse.json({ error: 'Invalid mediaKey' }, { status: 400 })
+      return NextResponse.json({ error: 'Invalid itemKey' }, { status: 400 })
     }
     const auth = await requireLibraryAccess(request, libraryId)
     if (auth instanceof NextResponse) return auth
 
-    return NextResponse.json(getResolvedTagsForItem(mediaKey))
+    return NextResponse.json(getResolvedTagsForItem(itemKey))
   } catch (err) {
     return NextResponse.json({ error: (err as Error).message }, { status: 500 })
   }
@@ -30,18 +30,18 @@ export async function GET(request: NextRequest) {
 
 export async function POST(request: NextRequest) {
   try {
-    const { mediaKey, tagId } = await request.json()
-    if (!mediaKey || !tagId) {
-      return NextResponse.json({ error: 'mediaKey and tagId are required' }, { status: 400 })
+    const { itemKey, tagId } = await request.json()
+    if (!itemKey || !tagId) {
+      return NextResponse.json({ error: 'itemKey and tagId are required' }, { status: 400 })
     }
-    const libraryId = extractLibraryId(mediaKey)
+    const libraryId = extractLibraryId(itemKey)
     if (!libraryId) {
-      return NextResponse.json({ error: 'Invalid mediaKey' }, { status: 400 })
+      return NextResponse.json({ error: 'Invalid itemKey' }, { status: 400 })
     }
     const auth = await requireLibraryAccess(request, libraryId)
     if (auth instanceof NextResponse) return auth
 
-    addTagToItem(mediaKey, tagId)
+    addTagToItem(itemKey, tagId)
     return new NextResponse(null, { status: 204 })
   } catch (err) {
     return NextResponse.json({ error: (err as Error).message }, { status: 400 })
@@ -51,19 +51,19 @@ export async function POST(request: NextRequest) {
 export async function DELETE(request: NextRequest) {
   try {
     const { searchParams } = new URL(request.url)
-    const mediaKey = searchParams.get('mediaKey')
+    const itemKey = searchParams.get('itemKey')
     const tagId = searchParams.get('tagId')
-    if (!mediaKey || !tagId) {
-      return NextResponse.json({ error: 'mediaKey and tagId are required' }, { status: 400 })
+    if (!itemKey || !tagId) {
+      return NextResponse.json({ error: 'itemKey and tagId are required' }, { status: 400 })
     }
-    const libraryId = extractLibraryId(mediaKey)
+    const libraryId = extractLibraryId(itemKey)
     if (!libraryId) {
-      return NextResponse.json({ error: 'Invalid mediaKey' }, { status: 400 })
+      return NextResponse.json({ error: 'Invalid itemKey' }, { status: 400 })
     }
     const auth = await requireLibraryAccess(request, libraryId)
     if (auth instanceof NextResponse) return auth
 
-    removeTagFromItem(mediaKey, tagId)
+    removeTagFromItem(itemKey, tagId)
     return new NextResponse(null, { status: 204 })
   } catch (err) {
     return NextResponse.json({ error: (err as Error).message }, { status: 400 })

src/app/api/tv/route.ts

@@ -74,7 +74,7 @@ export async function DELETE(request: NextRequest) {
     return NextResponse.json({ error: 'Failed to delete series directory' }, { status: 500 })
   }
 
-  removeAllAssignmentsForItem(`${libraryId}:${seriesId}`)
+  removeAllAssignmentsForItem(`${libraryId}:tv_series:${seriesId}`)
 
   return new NextResponse(null, { status: 204 })
 }