chore: update .env.example; remove deprecated DB_URL and GitHub OAuth fields

.env.example

@@ -1,7 +1,5 @@
-DB_URL="postgresql://user:password@db:5432/esports"
+ROOT_ADMIN_EMAIL=""
 
-# Drizzle
-# Replace with your DB credentials!
 DATABASE_URL="postgres://user:password@host:port/db-name"
 
 ORIGIN=""
@@ -10,18 +8,17 @@ ORIGIN=""
 # For production use 32 characters and generated with high entropy
 # https://www.better-auth.com/docs/installation
 BETTER_AUTH_SECRET=""
-# GitHub OAuth
-# https://www.better-auth.com/docs/authentication/github
-GITHUB_CLIENT_ID=""
-GITHUB_CLIENT_SECRET=""
+
+OSU_CLIENT_ID=""
+OSU_CLIENT_SECRET=""
 
 # Discord notifications
 DISCORD_BOT_TOKEN=""
 DISCORD_MATCH_CHANNEL_ID=""
 
 # Cloudflare R2 image storage
-R2_ACCOUNT_ID=""           # Your Cloudflare Account ID
-R2_ACCESS_KEY_ID=""        # R2 API token Access Key ID
-R2_SECRET_ACCESS_KEY=""    # R2 API token Secret Access Key
-R2_BUCKET=""               # Bucket name, e.g. vash-esports-images
-R2_PUBLIC_URL=""           # Public URL for the bucket, e.g. https://cdn.esports.vash.software
+R2_ACCOUNT_ID=""                                            # Your Cloudflare Account ID
+R2_ACCESS_KEY_ID=""                                         # R2 API token Access Key ID
+R2_SECRET_ACCESS_KEY=""                                     # R2 API token Secret Access Key
+R2_BUCKET="vash-esports-images"                             # Bucket name, e.g. vash-esports-images
+R2_PUBLIC_URL="https://cdn.esports.vash.software"           # Public URL for the bucket, e.g. https://cdn.esports.vash.software