feat: 10 quick wins — account deletion, health check, debug cleanup, UX polish, graceful shutdown

- backend/handlers/user/account.go: Wire DELETE /api/user/account to call
  anonymize_user() for registered users and delete_guest_user() for guests,
  with CardDAV contact cleanup
- backend/handlers/user/profile_test.go: Add TestAccount_DeleteGuest and
  enhance TestAccount_Delete to verify anonymization results
- backend/main.go: Add GET /api/health endpoint with DB ping and S3 status
  check; add HSTS and Referrer-Policy security headers; replace
  http.ListenAndServe with http.Server + graceful SIGTERM/SIGINT shutdown
- frontend/routes/+layout.svelte: Replace alert() with toast notifications
  for email verification flow
- frontend/routes/login/+page.svelte: Replace alert() with toast.info for
  social login prototype buttons
- frontend/booking/BookingFlow.svelte: Remove 2 console.log debug calls;
  add cancellation policy note in Step 3; add timezone policy comment
- frontend/ImageUpload.svelte: Comment out debug console.log
- init-scripts/init-script.sql: Add delete_guest_user() SQL function
- docs: Update README.md and Obsidian notes to reflect completed items

backend/handlers/user/account.go

@@ -1,12 +1,61 @@
 package user
 
 import (
+	"database/sql"
+	"fmt"
+	"log"
 	"net/http"
+
+	"crussell/db"
+	"crussell/internal/dav"
+	"crussell/mw"
 )
 
 // DELETE /api/user/account
 func DeleteAccountHandler(w http.ResponseWriter, r *http.Request) {
-	// TODO: Delete user's data
+	userID, ok := mw.GetUserID(r.Context())
+	if !ok {
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+		return
+	}
+
+	var accountRole string
+	err := db.DB.QueryRow(r.Context(), `SELECT account_role FROM users WHERE id = $1`, userID).Scan(&accountRole)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			http.Error(w, "user not found", http.StatusNotFound)
+			return
+		}
+		log.Printf("Failed to fetch user role for deletion: %v", err)
+		http.Error(w, "server error", http.StatusInternalServerError)
+		return
+	}
+
+	if accountRole == "guest" {
+		_, err = db.DB.Exec(r.Context(), `SELECT delete_guest_user($1)`, userID)
+		if err != nil {
+			log.Printf("Failed to delete guest user %s: %v", userID, err)
+			http.Error(w, "server error", http.StatusInternalServerError)
+			return
+		}
+	} else {
+		_, err = db.DB.Exec(r.Context(), `SELECT anonymize_user($1)`, userID)
+		if err != nil {
+			log.Printf("Failed to anonymize user %s: %v", userID, err)
+			http.Error(w, "server error", http.StatusInternalServerError)
+			return
+		}
+	}
+
+	// Delete CardDAV contact (non-blocking, best-effort)
+	if dav.Service != nil {
+		go func() {
+			uri := fmt.Sprintf("%s.vcf", userID)
+			if err := dav.Service.DeleteContact(1, uri); err != nil {
+				log.Printf("Warning: Failed to delete CardDAV contact for user %s: %v", userID, err)
+			}
+		}()
+	}
 
 	w.WriteHeader(http.StatusNoContent)
 }

backend/handlers/user/profile_test.go

@@ -239,7 +239,8 @@ func TestPasswordChange_InvalidNewPassword(t *testing.T) {
 	}
 }
 
-// TestAccount_Delete verifies that a user can delete their own account, returning 204 No Content.
+// TestAccount_Delete verifies that a registered user can delete their own account,
+// triggering anonymization and returning 204 No Content.
 func TestAccount_Delete(t *testing.T) {
 	cleanup, pool := setupTest(t)
 	defer cleanup()
@@ -262,6 +263,52 @@ func TestAccount_Delete(t *testing.T) {
 		t.Errorf("expected status 204, got %d", rr.Code)
 		t.Logf("response body: %s", rr.Body.String())
 	}
+
+	var firstName, accountRole string
+	err = pool.QueryRow(context.Background(), `SELECT n_first_name, account_role FROM users WHERE id = $1`, userID).Scan(&firstName, &accountRole)
+	if err != nil {
+		t.Fatalf("failed to query anonymized user: %v", err)
+	}
+	if firstName != "Deleted" {
+		t.Errorf("expected first name 'Deleted', got %q", firstName)
+	}
+	if accountRole != "guest" {
+		t.Errorf("expected account_role 'guest', got %q", accountRole)
+	}
+}
+
+// TestAccount_DeleteGuest verifies that a guest user is fully deleted.
+func TestAccount_DeleteGuest(t *testing.T) {
+	cleanup, pool := setupTest(t)
+	defer cleanup()
+
+	userID, err := fixtures.CreateTestGuestUser(pool)
+	if err != nil {
+		t.Fatalf("failed to create test guest user: %v", err)
+	}
+
+	token := jwt.GenerateUserToken(userID)
+
+	req := httptest.NewRequest(http.MethodDelete, "/api/user/account", nil)
+	req = req.WithContext(context.WithValue(context.Background(), mw.UserIDKey, userID))
+	req.Header.Set("Authorization", "Bearer "+token)
+
+	rr := httptest.NewRecorder()
+	DeleteAccountHandler(rr, req)
+
+	if rr.Code != http.StatusNoContent {
+		t.Errorf("expected status 204, got %d", rr.Code)
+		t.Logf("response body: %s", rr.Body.String())
+	}
+
+	var count int
+	err = pool.QueryRow(context.Background(), `SELECT COUNT(*) FROM users WHERE id = $1`, userID).Scan(&count)
+	if err != nil {
+		t.Fatalf("failed to query user count: %v", err)
+	}
+	if count != 0 {
+		t.Errorf("expected user to be deleted, found %d rows", count)
+	}
 }
 
 // TestLoyalty_Get verifies that a user can retrieve their loyalty stamps count and referral code.