fix(discord-gateway): skip migration if schema tables already exist

Instead of failing on CREATE TABLE when tables already exist, check
information_schema for all 10 schema tables. If all exist, skip
migration gracefully. This handles deployments where DB was created
by a previous deployment with different migration files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

services/discord-gateway/src/shared/database/migrate.ts

@@ -1,7 +1,7 @@
 import "dotenv/config";
 import { drizzle as drizzlePostgres } from "drizzle-orm/node-postgres";
 import { migrate as migratePostgres } from "drizzle-orm/node-postgres/migrator";
-import { config } from "../../shared/config/config.js";
+import type { PoolClient } from "pg";
 import { createChildLogger } from "../../shared/logger/logger.js";
 import {
   closeDatabase,
@@ -14,6 +14,30 @@ const logger = createChildLogger("migrate");
 const MIGRATION_LOCK_KEY_1 = 2026;
 const MIGRATION_LOCK_KEY_2 = 531;
 
+/**
+ * Check if all schema tables already exist in the database.
+ * If they do, the database was likely created by a previous deployment
+ * and migration is not needed.
+ */
+async function checkSchemaExists(client: PoolClient): Promise<boolean> {
+  try {
+    const result = await client.query(`
+      SELECT COUNT(*) as count
+      FROM information_schema.tables
+      WHERE table_schema = 'public'
+        AND table_name IN (
+          'ai_analysis_runs', 'attachments', 'message_reviews',
+          'messages', 'moderation_actions', 'muxer_jobs',
+          'retention_policies', 'text_analysis_cache', 'ui_state',
+          'voice_recordings'
+        )
+    `);
+    return result.rows[0]?.count === "10";
+  } catch {
+    return false;
+  }
+}
+
 export async function runMigrations(): Promise<void> {
   try {
     logger.info("Starting PostgreSQL migrations");
@@ -29,6 +53,13 @@ export async function runMigrations(): Promise<void> {
         ]);
 
         try {
+          // If all schema tables already exist, skip migration
+          const schemaExists = await checkSchemaExists(client);
+          if (schemaExists) {
+            logger.info("Schema tables already exist; skipping migration");
+            return;
+          }
+
           await migratePostgres(db, {
             migrationsFolder: "./drizzle/migrations",
           });