chore: update environment configuration and build outputs

- Added new output path for build artifacts in turbo.json to include "build/**".
- Updated .env.example to include required environment variables for database and Redis connections, enhancing clarity for setup.
- Refined self-hosting documentation to ensure accurate configuration for public server URLs and object storage options.

turbo.json

@@ -7,7 +7,7 @@
     },
     "build": {
       "dependsOn": ["^build"],
-      "outputs": [".next/**", "!.next/cache/**", ".svelte-kit/**", ".vercel/**", "dist/**"]
+      "outputs": [".next/**", "!.next/cache/**", ".svelte-kit/**", ".vercel/**", "dist/**", "build/**"]
     },
     "start": {
       "cache": false,