refactor(config): add env parsing helpers and tighten startup validation

.env.example

@@ -9,6 +9,9 @@ DATABASE_URL="postgresql://postgres:postgres@localhost:5432/friendolls_dev?schem
 # Redis
 REDIS_HOST=localhost
 REDIS_PORT=6379
+REDIS_REQUIRED=false
+REDIS_CONNECT_TIMEOUT_MS=5000
+REDIS_STARTUP_RETRIES=10
 
 # JWT Configuration
 JWT_SECRET=replace-with-strong-random-secret