Add per-user library settings, folder passwords, and a still picker.

Settings manages folders, thumbnail defaults, and passwords for the signed-in account, and choosing an image now browses saved stills instead of only the desktop file dialog.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/api/library/stills/[id].delete.ts

@@ -0,0 +1,8 @@
+export default defineEventHandler(async (event) => {
+  const { owner } = assertLibraryOwner(event)
+  const id = String(getRouterParam(event, 'id') || '')
+  const still = getStill(owner, id)
+  assertFolderAccess(event, still.folderId)
+  await deleteStill(owner, id)
+  return publicLibrary(event)
+})