fix some custom room authoring issues

apps/img/migrations/0002_image_interaction.sql

@@ -0,0 +1,15 @@
+-- A player's interaction with a saved image — one row per (player, image). Only
+-- `cheered` for now; named generically so other per-user interactions (e.g.
+-- favorited) can be added as columns later. Written by the `api` worker's cheer
+-- endpoints (/api/images/v1/cheer, /api/images/v5/cheered/bulk), which also keeps
+-- the image's denormalized CheerCount in sync from it. Generated from
+-- src/images-db.ts (SCHEMA_DDL) — keep in sync.
+
+CREATE TABLE IF NOT EXISTS image_interaction (
+  player_id INTEGER NOT NULL,
+  saved_image_id INTEGER NOT NULL,
+  cheered INTEGER NOT NULL DEFAULT 0,
+  created_at TEXT,
+  PRIMARY KEY (player_id, saved_image_id)
+  );
+CREATE INDEX IF NOT EXISTS idx_image_interaction_image ON image_interaction (saved_image_id);