refactor: code efficiency improvements (Issues #9-13, #15, #17-20)

Backend:
- Extract shared hard-delete authorization utility (#9)
- Extract Prisma include constants per entity (#11)
- Fix N+1 query pattern in events findAll (#12)
- Extract shared date utility functions (#13)
- Move vehicle utilization filtering to DB query (#15)
- Add ParseBooleanPipe for query params
- Add CurrentDriver decorator + ResolveDriverInterceptor (#20)

Frontend:
- Extract shared form utilities (toDatetimeLocal) and enum labels (#17)
- Replace browser confirm() with styled ConfirmModal (#18)
- Add centralized query-keys.ts constants (#19)
- Clean up unused imports, add useMemo where needed (#19)
- Standardize filter button styling across list pages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/hooks/useSignalMessages.ts

@@ -1,5 +1,6 @@
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { api } from '../lib/api';
+import { queryKeys } from '../lib/query-keys';
 
 export interface SignalMessage {
   id: string;
@@ -19,7 +20,7 @@ export interface UnreadCounts {
  */
 export function useDriverMessages(driverId: string | null, enabled = true) {
   return useQuery({
-    queryKey: ['signal-messages', driverId],
+    queryKey: driverId ? queryKeys.signal.messages(driverId) : ['signal-messages', null],
     queryFn: async () => {
       if (!driverId) return [];
       const { data } = await api.get<SignalMessage[]>(`/signal/messages/driver/${driverId}`);
@@ -35,7 +36,7 @@ export function useDriverMessages(driverId: string | null, enabled = true) {
  */
 export function useUnreadCounts() {
   return useQuery({
-    queryKey: ['signal-unread-counts'],
+    queryKey: queryKeys.signal.unreadCounts,
     queryFn: async () => {
       const { data } = await api.get<UnreadCounts>('/signal/messages/unread');
       return data;
@@ -54,8 +55,10 @@ export function useDriverResponseCheck(
   // Only include events that have a driver
   const eventsWithDrivers = events.filter((e) => e.driver?.id);
 
+  const eventIds = eventsWithDrivers.map((e) => e.id).join(',');
+
   return useQuery({
-    queryKey: ['signal-driver-responses', eventsWithDrivers.map((e) => e.id).join(',')],
+    queryKey: queryKeys.signal.driverResponses(eventIds),
     queryFn: async () => {
       if (eventsWithDrivers.length === 0) {
         return new Set<string>();
@@ -97,11 +100,11 @@ export function useSendMessage() {
     onSuccess: (data, variables) => {
       // Add the new message to the cache immediately
       queryClient.setQueryData<SignalMessage[]>(
-        ['signal-messages', variables.driverId],
+        queryKeys.signal.messages(variables.driverId),
         (old) => [...(old || []), data]
       );
       // Also invalidate to ensure consistency
-      queryClient.invalidateQueries({ queryKey: ['signal-messages', variables.driverId] });
+      queryClient.invalidateQueries({ queryKey: queryKeys.signal.messages(variables.driverId) });
     },
   });
 }
@@ -120,7 +123,7 @@ export function useMarkMessagesAsRead() {
     onSuccess: (_, driverId) => {
       // Update the unread counts cache
       queryClient.setQueryData<UnreadCounts>(
-        ['signal-unread-counts'],
+        queryKeys.signal.unreadCounts,
         (old) => {
           if (!old) return {};
           const updated = { ...old };
@@ -130,7 +133,7 @@ export function useMarkMessagesAsRead() {
       );
       // Mark messages as read in the messages cache
       queryClient.setQueryData<SignalMessage[]>(
-        ['signal-messages', driverId],
+        queryKeys.signal.messages(driverId),
         (old) => old?.map((msg) => ({ ...msg, isRead: true })) || []
       );
     },