feat: introduce web dashboard with multi-bot management

- add Discord OAuth2 authentication
- allow users to register their bots via token
- implement dynamic bot start/stop system
- store bots in database (multi-tenant)
- replace single-bot env setup with scalable architecture

.env.example

@@ -1,26 +1,31 @@
-DISCORD_TOKEN=
-DISCORD_CLIENT_ID=
-DATABASE_URL=postgresql://discord_bot:CHANGE_ME_STRONG_PASSWORD@localhost:5432/discord_bots
-DATABASE_SSL=false
-DATABASE_SSL_REJECT_UNAUTHORIZED=true
-DATABASE_SSL_CA=
-ALLOW_INSECURE_DB_SSL=false
-PRESENCE_STREAM_URL=https://twitch.tv/discord
-POSTGRES_DB=discord_bots
-POSTGRES_USER=discord_bot
+NODE_ENV=development
+
+# Shared infrastructure
+POSTGRES_DB=discord_saas
+POSTGRES_USER=discord_saas
 POSTGRES_PASSWORD=CHANGE_ME_STRONG_POSTGRES_PASSWORD
-REDIS_PASSWORD=CHANGE_ME_STRONG_REDIS_PASSWORD
 POSTGRES_PORT=5432
-PREFIX=+
-DEFAULT_LANG=en
-DEV_GUILD_ID=
-AUTO_DEPLOY_SLASH=false
-LOG_LEVEL=info
-STATE_BACKEND=memory
-REDIS_URL=
-COMMAND_DISPATCH_MODE=local
-COMMAND_QUEUE_NAME=bot:${botId}:command-jobs
-GLOBAL_RATE_LIMIT_MAX_REQUESTS=20
-GLOBAL_RATE_LIMIT_WINDOW_SECONDS=10
-RATE_LIMIT_FAIL_OPEN=false
-ENABLE_LEADER_ELECTION=true
+REDIS_PASSWORD=CHANGE_ME_STRONG_REDIS_PASSWORD
+DATABASE_URL=postgresql://discord_saas:CHANGE_ME_STRONG_POSTGRES_PASSWORD@localhost:5432/discord_saas
+DATABASE_SSL=false
+
+# OAuth2 + auth API
+DISCORD_CLIENT_ID=
+DISCORD_CLIENT_SECRET=
+DISCORD_REDIRECT_URI=http://localhost:4000/auth/discord/callback
+JWT_SECRET=CHANGE_ME_LONG_RANDOM_SECRET
+JWT_EXPIRES_IN=7d
+SESSION_COOKIE_NAME=saas_session
+COOKIE_SECURE=false
+WEB_URL=http://localhost:3000
+API_BASE_URL=http://localhost:4000
+
+# Encryption key for bot tokens (32 bytes base64)
+TOKEN_ENCRYPTION_KEY=REPLACE_WITH_32_BYTE_BASE64_KEY
+
+# Multi-tenant API limits
+TENANT_RATE_LIMIT_MAX=120
+TENANT_RATE_LIMIT_WINDOW_SECONDS=60
+
+# Web
+NEXT_PUBLIC_API_BASE_URL=http://localhost:4000