feat: support self-host docker build (#5506)

Test command: `docker compose -f ./.github/deployment/self-host/compose.yaml up`

packages/backend/server/src/prelude.ts

@@ -1,5 +1,17 @@
+import { homedir } from 'node:os';
+import { join } from 'node:path';
+
+import { config } from 'dotenv';
+
+import { SERVER_FLAVOR } from './config/default';
+
+if (SERVER_FLAVOR === 'selfhosted') {
+  config({ path: join(homedir(), '.affine', '.env') });
+} else {
+  config();
+}
+
 import 'reflect-metadata';
-import 'dotenv/config';
 import './affine';
 import './affine.config';