refactor: move auth, GDPR, and booking cleanup to centralized scheduler

Convert CleanupRevokedJTIs to return (int, error) and remove StartJTICleanup goroutine. Add CleanupStaleLoginEntries and CleanupGDPRExportCache for centralized scheduler. Add clock.London timezone location.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/handlers/auth/local.go

@@ -1,10 +1,10 @@
 package auth
 
 import (
+	"context"
 	"crussell/auth"
 	"crussell/clock"
 	"crussell/db"
-	"github.com/jackc/pgx/v5"
 	"crussell/internal/dav"
 	"crussell/internal/validators"
 	"crussell/internal/zxcvbnjs"
@@ -16,21 +16,22 @@ import (
 	"log"
 	"net/http"
 
-	"github.com/go-chi/chi/v5/middleware"
+	"github.com/jackc/pgx/v5"
+
 	"os"
 	"regexp"
 	"strings"
 	"sync"
 	"time"
 
+	"github.com/go-chi/chi/v5/middleware"
+
 	"github.com/nyaruka/phonenumbers"
 	"golang.org/x/crypto/bcrypt"
 	"golang.org/x/text/cases"
 	"golang.org/x/text/language"
 )
 
-
-
 const maxLoginInProgress = 20
 
 // Login state management
@@ -39,30 +40,18 @@ var (
 	loginInProgress = make(map[string]time.Time)
 )
 
-func init() {
-	go func() {
-		ticker := time.NewTicker(1 * time.Hour)
-		defer ticker.Stop()
-
-		for range ticker.C {
-			func() {
-				defer func() {
-					if r := recover(); r != nil {
-						log.Printf("Panic recovered in login state cleanup ticker: %v", r)
-					}
-				}()
-				loginStateMu.Lock()
-				now := clock.Now()
-				// Clean up stuck loginInProgress entries (older than 30s)
-				for userID, startedAt := range loginInProgress {
-					if now.Sub(startedAt) > 30*time.Second {
-						delete(loginInProgress, userID)
-					}
-				}
-				loginStateMu.Unlock()
-			}()
+// CleanupStaleLoginEntries removes stuck loginInProgress entries older than 30 seconds.
+// Called by the centralised jobs scheduler.
+func CleanupStaleLoginEntries(ctx context.Context) (int, error) {
+	loginStateMu.Lock()
+	defer loginStateMu.Unlock()
+	now := clock.Now()
+	for userID, startedAt := range loginInProgress {
+		if now.Sub(startedAt) > 30*time.Second {
+			delete(loginInProgress, userID)
 		}
-	}()
+	}
+	return 0, nil
 }
 
 type RegisterRequest struct {