feat(auth): add Discord OAuth sign-in and user timezones

Add persistent user and session storage, protected profile requests, and React sign-in controls. Capture and preserve each user's timezone, and load development and production configuration before migrations and server startup.

.gitignore

@@ -26,12 +26,11 @@ logs
 _.log
 report.[0-9]_.[0-9]_.[0-9]_.[0-9]_.json
 
-# dotenv environment variable files
+# dotenv files may contain credentials; commit only example templates.
 .env
-.env.development.local
-.env.test.local
-.env.production.local
-.env.local
+.env.*
+!.env.example
+!.env.*.example
 
 # caches
 .eslintcache