feat: scheduled announcements — /announce command (#42)

config.json

@@ -119,7 +119,8 @@
       "lock": "admin",
       "unlock": "admin",
       "slowmode": "admin",
-      "modlog": "moderator"
+      "modlog": "moderator",
+      "announce": "moderator"
     }
   }
 }

migrations/002_scheduled-messages.cjs

@@ -0,0 +1,35 @@
+/**
+ * Add scheduled_messages table for /announce command.
+ * Supports one-time and recurring (cron) scheduled messages.
+ *
+ * @see https://github.com/VolvoxLLC/volvox-bot/issues/42
+ */
+
+/** @param {import('node-pg-migrate').MigrationBuilder} pgm */
+exports.up = (pgm) => {
+  pgm.sql(`
+    CREATE TABLE IF NOT EXISTS scheduled_messages (
+      id SERIAL PRIMARY KEY,
+      guild_id TEXT NOT NULL,
+      channel_id TEXT NOT NULL,
+      content TEXT NOT NULL,
+      embed_json JSONB,
+      cron_expression TEXT,
+      next_run TIMESTAMPTZ NOT NULL,
+      timezone TEXT NOT NULL DEFAULT 'America/New_York',
+      author_id TEXT NOT NULL,
+      enabled BOOLEAN NOT NULL DEFAULT true,
+      one_time BOOLEAN NOT NULL DEFAULT false,
+      created_at TIMESTAMPTZ DEFAULT NOW()
+    )
+  `);
+
+  pgm.sql(
+    'CREATE INDEX IF NOT EXISTS idx_scheduled_next_run ON scheduled_messages(next_run) WHERE enabled = true',
+  );
+};
+
+/** @param {import('node-pg-migrate').MigrationBuilder} pgm */
+exports.down = (pgm) => {
+  pgm.sql('DROP TABLE IF EXISTS scheduled_messages CASCADE');
+};