feat: replace Redis with DragonflyDB

- Replace Redis server with DragonflyDB v1.40.1 (Redis protocol compatible)
- Stop redis-server service, enable dragonfly service on 127.0.0.1:6379
- Configure dragonfly in /etc/dragonfly/dragonfly.conf (bind 127.0.0.1, maxmemory 2gb)
- Update .env: remove REDIS_URL reference

Improve database reliability:
- Fix catalog-tree.ts: remove CAST(page_id AS CHAR) to enable index usage (122 rows vs 78k full scan)
- Fix catalog-repair.ts: replace sql.raw() string interpolation with parameterized sql queries using quoteIdentifier()
- Improve redis retry resilience: change retryStrategy to not give up after 3 attempts, enabling automatic reconnect after server restart

Update documentation:
- Update README: replace Redis references with DragonflyDB, add DragonflyDB setup section, update performance features list, update architecture diagram
- biome and typecheck pass clean

src/lib/redis.ts

@@ -24,8 +24,7 @@ function createRedis(): Redis | null {
 		const client = new Redis(url, {
 			maxRetriesPerRequest: 3,
 			retryStrategy(times) {
-				if (times > 3) return null;
-				return Math.min(times * 200, 2000);
+				return Math.min(times * 200, 5000);
 			},
 			lazyConnect: true,
 		});