feat: migrate to DragonflyDB and clean up environment configuration

- Replace Redis with DragonflyDB for better performance and memory efficiency
- Remove redundant environment variables (POSTGRES_*, ENCRYPTION_KEY, OAUTH_SERVICE_URL)
- Consolidate database configuration to use single DB_* variables
- Use JWT_SECRET for both JWT tokens and encryption
- Remove PORT variable redundancy, use BACKEND_PORT consistently
- Clean up docker-compose configurations for dev/prod consistency
- Add DragonflyDB configuration with optimized memory usage
- Remove redis.conf as it's no longer needed
- Update health checks to use Redis-compatible CLI for DragonflyDB
- Add missing VITE_API_URL to production frontend
- Fix GitHub Actions to use correct go.sum path
- Clean up development directories and unused files

backend/queries/users.sql

@@ -0,0 +1,38 @@
+-- name: GetUserByID :one
+SELECT id, email, first_name, last_name, avatar_url, is_active, is_verified, last_login, created_at, updated_at
+FROM users
+WHERE id = $1 LIMIT 1;
+
+-- name: GetUserByEmail :one
+SELECT id, email, first_name, last_name, avatar_url, is_active, is_verified, last_login, created_at, updated_at
+FROM users
+WHERE email = $1 LIMIT 1;
+
+-- name: CreateUser :one
+INSERT INTO users (email, password_hash, first_name, last_name, avatar_url, is_active, is_verified)
+VALUES ($1, $2, $3, $4, $5, $6, $7)
+RETURNING id, email, first_name, last_name, avatar_url, is_active, is_verified, last_login, created_at, updated_at;
+
+-- name: UpdateUser :one
+UPDATE users
+SET first_name = $2,
+    last_name = $3,
+    avatar_url = $4,
+    is_active = $5,
+    updated_at = CURRENT_TIMESTAMP
+WHERE id = $1
+RETURNING id, email, first_name, last_name, avatar_url, is_active, is_verified, last_login, created_at, updated_at;
+
+-- name: UpdateLastLogin :exec
+UPDATE users
+SET last_login = CURRENT_TIMESTAMP
+WHERE id = $1;
+
+-- name: DeleteUser :exec
+DELETE FROM users WHERE id = $1;
+
+-- name: ListUsers :many
+SELECT id, email, first_name, last_name, avatar_url, is_active, is_verified, last_login, created_at, updated_at
+FROM users
+ORDER BY created_at DESC
+LIMIT $1 OFFSET $2;