Revert "fix(bookmarks): upsert on title conflict so position upgrades don't 500"

This reverts commit 27b3dcb69f.

internal/database/queries/queries.sql

@@ -893,10 +893,6 @@ ORDER BY deleted ASC, deleted_at DESC NULLS LAST
 LIMIT 1;
 
 -- name: CreateMediaBookmarkFull :one
--- The dedup key can change while the title stays the same (e.g. a client
--- upgrading a bookmark from percentage-only to a CFI position), so the
--- title UNIQUE constraint races the dedup-key lookup. Upsert on the title
--- slot: the conflicting row is by definition the same bookmark.
 INSERT INTO media_bookmarks (
     media_item_id, user_id, page_number, chapter_number,
     cfi_position, title, position, notes,
@@ -905,23 +901,7 @@ INSERT INTO media_bookmarks (
     device_sync_data
 ) VALUES (
     $1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15
-) ON CONFLICT (media_item_id, user_id, title) DO UPDATE SET
-    page_number = EXCLUDED.page_number,
-    chapter_number = EXCLUDED.chapter_number,
-    cfi_position = EXCLUDED.cfi_position,
-    position = EXCLUDED.position,
-    notes = EXCLUDED.notes,
-    percentage_location = EXCLUDED.percentage_location,
-    epubcfi_location = EXCLUDED.epubcfi_location,
-    chapter_reference = EXCLUDED.chapter_reference,
-    dedup_key = EXCLUDED.dedup_key,
-    last_modified_at = EXCLUDED.last_modified_at,
-    last_modified_source = EXCLUDED.last_modified_source,
-    device_sync_data = EXCLUDED.device_sync_data,
-    created_at = created_at,
-    deleted = FALSE,
-    deleted_at = NULL
-RETURNING *;
+) RETURNING *;
 
 -- name: UpdateMediaBookmarkForSync :one
 UPDATE media_bookmarks SET