feat(db): archive lifecycle schema and queries for missing media

Add the storage behind the archive-instead-of-delete lifecycle:

- media_items.missing_scan_count (INT, default 0) and archived_at
  (TIMESTAMPTZ, partial index), both as idempotent ADD COLUMN IF NOT
  EXISTS backfills for existing installs.
- MarkMediaItemMissing / ArchiveMediaItem / ClearMediaItemArchive plus
  PurgeExpiredArchivedMediaItems (retention cutoff) and
  PurgeAllArchivedMediaItems (manual bulk), with CountArchivedMediaItems
  for the admin UI.
- Archived items are hidden from every user-facing listing:
  ListMediaItems, ListMediaItemsByLibrary, ListMediaItemsSorted,
  SearchMediaItems, SearchMediaItemsUnified, the next_books CTE, the
  library media counts, and the search autocomplete value lists. Detail
  lookups by id/path/sha are intentionally unfiltered, and a dedicated
  ListMediaItemsByLibraryIncludingArchived feeds the scanner so the
  lifecycle pass can see and restore archived rows.

internal/database/querier.go

@@ -20,6 +20,9 @@ type Querier interface {
 	AddBookToKoboShelf(ctx context.Context, arg AddBookToKoboShelfParams) (KoboShelves, error)
 	// Library Folders queries
 	AddLibraryFolder(ctx context.Context, arg AddLibraryFolderParams) (LibraryFolders, error)
+	// Second consecutive missing scan: hide the item from all browsing while
+	// preserving reading history in case the file returns.
+	ArchiveMediaItem(ctx context.Context, id pgtype.UUID) error
 	// Bulk update format group for all media items
 	BulkUpdateFormatGroups(ctx context.Context) error
 	BulkUpdateProgressFromSync(ctx context.Context, arg BulkUpdateProgressFromSyncParams) ([]interface{}, error)
@@ -30,10 +33,14 @@ type Querier interface {
 	ClearDeviceSyncQueue(ctx context.Context, deviceID pgtype.UUID) error
 	ClearKoboShelf(ctx context.Context, deviceID pgtype.UUID) error
 	ClearKoboShelfByName(ctx context.Context, arg ClearKoboShelfByNameParams) error
+	// File is back on disk (by path or content hash): restore visibility and
+	// reset the missing-scan counter. No-op for items that were never archived.
+	ClearMediaItemArchive(ctx context.Context, id pgtype.UUID) error
 	// Reset an item to scanned defaults: clears per-field user overrides so the
 	// next rescan can freely overwrite user-customized metadata.
 	ClearMediaItemMetadataOverrides(ctx context.Context, id pgtype.UUID) error
 	CountAdmins(ctx context.Context) (int64, error)
+	CountArchivedMediaItems(ctx context.Context) (int64, error)
 	// Count unlinked books for a device
 	CountUnlinkedBooks(ctx context.Context, deviceID pgtype.UUID) (int64, error)
 	CountUserDevices(ctx context.Context, userID pgtype.UUID) (int64, error)
@@ -343,6 +350,7 @@ type Querier interface {
 	ListLibraries(ctx context.Context) ([]ListLibrariesRow, error)
 	ListMediaItems(ctx context.Context, arg ListMediaItemsParams) ([]ListMediaItemsRow, error)
 	ListMediaItemsByLibrary(ctx context.Context, libraryID pgtype.UUID) ([]ListMediaItemsByLibraryRow, error)
+	ListMediaItemsByLibraryIncludingArchived(ctx context.Context, libraryID pgtype.UUID) ([]ListMediaItemsByLibraryIncludingArchivedRow, error)
 	// List all media items sharing a SHA-256 hash within a library (hash conflict group)
 	ListMediaItemsBySHA256AndLibrary(ctx context.Context, arg ListMediaItemsBySHA256AndLibraryParams) ([]MediaItems, error)
 	// List media items that have no stored SHA-256 (imported before hashing existed)
@@ -356,6 +364,13 @@ type Querier interface {
 	// List unresolved unlinked books with pagination
 	ListUnresolvedUnlinkedBooks(ctx context.Context, arg ListUnresolvedUnlinkedBooksParams) ([]ListUnresolvedUnlinkedBooksRow, error)
 	ListUsers(ctx context.Context) ([]ListUsersRow, error)
+	// First consecutive scan that cannot find the file on disk.
+	MarkMediaItemMissing(ctx context.Context, id pgtype.UUID) error
+	// Manual bulk purge from the library admin page.
+	PurgeAllArchivedMediaItems(ctx context.Context) ([]PurgeAllArchivedMediaItemsRow, error)
+	// Retention sweep at library-scan time: hard-delete archived items older
+	// than the cutoff. Cascades remove reading history with the row.
+	PurgeExpiredArchivedMediaItems(ctx context.Context, archivedAt pgtype.Timestamptz) ([]PurgeExpiredArchivedMediaItemsRow, error)
 	PurgeExpiredBookmarkTombstones(ctx context.Context, deletedAt pgtype.Timestamptz) error
 	PurgeExpiredHighlightTombstones(ctx context.Context, deletedAt pgtype.Timestamptz) error
 	PurgeExpiredNoteTombstones(ctx context.Context, deletedAt pgtype.Timestamptz) error