refactor(db): replace sqlc with handwritten pgx repos

- Finish Paddle-to-Stripe billing migration; drop paddle/stripe libs
- Renumber migrations; add 00012 memberships+manage_token,
  00013 location_type_capacity
- Add tests: admin, auth, bookings customer service
- Remove graphify-out artifacts and stale env files

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/internal/httpx/middleware.go

@@ -25,10 +25,11 @@ type visitor struct {
 }
 
 type RateLimiter struct {
-	mu       sync.Mutex
-	visitors map[string]*visitor
-	limit    rate.Limit
-	burst    int
+	mu          sync.Mutex
+	visitors    map[string]*visitor
+	limit       rate.Limit
+	burst       int
+	cleanupOnce sync.Once
 }
 
 func NewRateLimiter(limit rate.Limit, burst int) *RateLimiter {
@@ -40,7 +41,9 @@ func NewRateLimiter(limit rate.Limit, burst int) *RateLimiter {
 }
 
 func (r *RateLimiter) Middleware() gin.HandlerFunc {
-	go r.cleanupLoop()
+	r.cleanupOnce.Do(func() {
+		go r.cleanupLoop()
+	})
 
 	return func(c *gin.Context) {
 		ip := c.ClientIP()