fix: panic recovery, rate limiting, transaction error handling, pagination

Hardening pass over the API surface. No route's auth requirements change.

Resilience:
- Add recover middleware. There was none, so an unhandled panic in any
  handler propagated out of the process instead of becoming a 500.
- Add a centralized ErrorHandler so errors and recovered panics return the
  same {success,message} envelope as the utils helpers, not Fiber's default
  plain-text body. 5xx responses are logged with method and path.

Rate limiting:
- Global 300/min per IP as an abuse backstop, exempting health/readiness
  probes and websocket upgrades.
- 10/min shared across every credential endpoint (customer/miler/admin/hub
  login, verify-pin, reset-pin, email OTP). PINs are 4 digits, so the whole
  keyspace was previously walkable in seconds. One shared limiter instance
  means rotating between endpoints doesn't reset the budget.
- Add TRUSTED_PROXIES config. Limits key on c.IP(), which behind a TLS
  terminator is the proxy, collapsing every client into one bucket. When set,
  X-Forwarded-For is honoured only from those proxies so the header can't be
  spoofed to dodge the limit. Logs a warning when unset.

Transactions:
- Check the error on all 51 previously-unchecked tx.Save/Create/Delete/
  Model(...).Update/Commit calls across 6 controllers. A failed write inside
  a transaction was silently ignored and the request still reported success;
  an unchecked Commit could fail with the caller told everything worked.
  Each site now rolls back and returns a specific message.

Pagination:
- Add utils.ParsePage/Paginated, reusing the pageno/pagesize convention
  GetAdminBookings already established. Default 500, hard cap 1000.
- Apply to the previously unbounded consignments, tripsheets, exceptions,
  app-users and clients endpoints. Defaults are high so existing consoles
  that don't paginate keep working; the cap only stops a growing table from
  being loaded wholesale. total is now a real COUNT, not len(data).
- GetClients also loaded the entire auth table to join in memory; it now
  fetches only the current page's rows.

Tests (first in the repo):
- Extract the hyperlocal pincode rule out of BookingPickupComplete into
  isHyperlocal so it is testable, covering the short/empty pincode fallback.
- Cover calculateVolumetricWeight and the ParsePage clamping rules.

Repo hygiene:
- Tag scratch/*.go with //go:build ignore. Each declared its own main(), so
  `go build ./...` failed on redeclaration; it now passes repo-wide.
- Untrack scratch/node_modules (216 files) and ignore node_modules, test
  artifacts, and the `doormile` binary `go build .` emits.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

controllers/clientController.go

@@ -119,20 +119,39 @@ func RegisterClient(c *fiber.Ctx) error {
 		role = auth.Role
 	}
 
-	tx.Commit()
+	if err := tx.Commit().Error; err != nil {
+		return utils.Internal(c, "failed to register client")
+	}
 
 	return utils.Created(c, buildClientResponse(client, email, role))
 }
 
 func GetClients(c *fiber.Ctx) error {
+	page := utils.ParsePage(c)
+
+	var total int64
+	if err := db.DB.Model(&models.DoormileClient{}).Count(&total).Error; err != nil {
+		return utils.Internal(c, "failed to count clients")
+	}
+
 	var clients []models.DoormileClient
-	if err := db.DB.Find(&clients).Error; err != nil {
+	if err := page.Apply(db.DB).Find(&clients).Error; err != nil {
 		return utils.Internal(c, "failed to fetch clients")
 	}
 
-	// Bulk load auth records once and map by client_id for O(1) lookup
+	// Bulk load auth records for just this page's clients, rather than the
+	// whole auth table, and map by client_id for O(1) lookup.
+	clientIDs := make([]uint64, 0, len(clients))
+	for _, client := range clients {
+		clientIDs = append(clientIDs, client.ID)
+	}
+
 	var auths []models.DoormileAuth
-	db.DB.Find(&auths)
+	if len(clientIDs) > 0 {
+		if err := db.DB.Where("client_id IN ?", clientIDs).Find(&auths).Error; err != nil {
+			return utils.Internal(c, "failed to fetch client credentials")
+		}
+	}
 	authByClientID := make(map[uint64]models.DoormileAuth, len(auths))
 	for _, a := range auths {
 		if a.ClientID != nil {
@@ -146,7 +165,7 @@ func GetClients(c *fiber.Ctx) error {
 		responses = append(responses, buildClientResponse(client, auth.Email, auth.Role))
 	}
 
-	return utils.List(c, responses, int64(len(responses)))
+	return utils.Paginated(c, responses, total, page)
 }
 
 func GetClientDetails(c *fiber.Ctx) error {
@@ -304,7 +323,9 @@ func UpdateClient(c *fiber.Ctx) error {
 		}
 	}
 
-	tx.Commit()
+	if err := tx.Commit().Error; err != nil {
+		return utils.Internal(c, "failed to update client")
+	}
 
 	return utils.OK(c, buildClientResponse(client, email, role))
 }
@@ -332,7 +353,9 @@ func DeleteClient(c *fiber.Ctx) error {
 		return utils.Internal(c, "failed to delete client")
 	}
 
-	tx.Commit()
+	if err := tx.Commit().Error; err != nil {
+		return utils.Internal(c, "failed to delete client")
+	}
 
 	return utils.Message(c, "client deleted successfully")
 }