feat(sync): propagate KOReader annotation deletions + history API

KOReader push (processBookAnnotations) accepts deleted_highlights and
deleted_bookmarks arrays of dedup keys and tombstones the matching rows,
after the upserts so a key present in both lists resolves to 'deleted'
(the newer intent). Deletions remain soft: rows stay restorable from the
history and echo to other devices as tombstones on their next pull. A
stale device replay of the annotation cannot resurrect the tombstone —
device pushes carry no modification timestamp, so the save loses to the
delete. Absence from these arrays is never a delete, keeping category
toggles safe.

New annotation-history endpoints (annotation_history.go, media.go):
  GET    /api/media-items/:id/annotations/deleted
  POST   /api/media-items/:id/annotations/:annotationId/restore
  DELETE /api/media-items/:id/annotations/:annotationId
All scoped to the authenticated user and the route's book; the DELETE is
the permanent purge (annotation_type required in query or body).

MediaDetail gains DeletedAnnotations, populated by the book page route
via the shared DeletedAnnotationsForBook builder, so the server-rendered
history ships with the page instead of requiring a client round-trip.

Binding tests cover the plugin's exact wire shape and the legacy
plugin case (arrays omitted -> empty).

internal/router/frontend.go

@@ -1329,13 +1329,14 @@ func registerFrontendRoutes(cfg *Config) {
 
 		// Assemble response (no field duplication!)
 		detail := handlers.MediaDetail{
-			MediaItems:      mediaItem, // Embedded - ALL fields available
-			Rating:          rating,
-			Collections:     collections,
-			ReadingProgress: progress,
-			ActiveConflict:  activeConflict,
-			NotesCount:      len(notes),
-			HighlightsCount: len(highlights),
+			MediaItems:         mediaItem, // Embedded - ALL fields available
+			Rating:             rating,
+			Collections:        collections,
+			ReadingProgress:    progress,
+			ActiveConflict:     activeConflict,
+			NotesCount:         len(notes),
+			HighlightsCount:    len(highlights),
+			DeletedAnnotations: handlers.DeletedAnnotationsForBook(c.Request().Context(), cfg.Queries, pgUserID, pgMediaUUID),
 		}
 
 		// Render template