RBAC: Enforce read-only viewer role across backend and frontend

- Add global WriteAccessGuard that blocks POST/PUT/PATCH/DELETE for viewer role
- Add @AllowViewer() decorator for endpoints viewers need (switch-org, intro-seen, AI recommendations)
- Add useIsReadOnly hook to auth store for frontend role checks
- Hide write UI (add/edit/delete/import buttons, inline editors) in all 13 data pages for viewers
- Disable inline NumberInputs on Budgets and Monthly Actuals pages for viewers
- Skip onboarding wizard for viewer role users

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

frontend/src/pages/reserves/ReservesPage.tsx

@@ -11,6 +11,7 @@ import { notifications } from '@mantine/notifications';
 import { IconPlus, IconEdit } from '@tabler/icons-react';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import api from '../../services/api';
+import { useIsReadOnly } from '../../stores/authStore';
 
 interface ReserveComponent {
   id: string; name: string; category: string; description: string;
@@ -26,6 +27,7 @@ export function ReservesPage() {
   const [opened, { open, close }] = useDisclosure(false);
   const [editing, setEditing] = useState<ReserveComponent | null>(null);
   const queryClient = useQueryClient();
+  const isReadOnly = useIsReadOnly();
 
   const { data: components = [], isLoading } = useQuery<ReserveComponent[]>({
     queryKey: ['reserve-components'],
@@ -89,7 +91,7 @@ export function ReservesPage() {
     <Stack>
       <Group justify="space-between">
         <Title order={2}>Reserve Components</Title>
-        <Button leftSection={<IconPlus size={16} />} onClick={() => { setEditing(null); form.reset(); open(); }}>Add Component</Button>
+        {!isReadOnly && <Button leftSection={<IconPlus size={16} />} onClick={() => { setEditing(null); form.reset(); open(); }}>Add Component</Button>}
       </Group>
       <SimpleGrid cols={{ base: 1, sm: 3 }}>
         <Card withBorder p="md">
@@ -139,7 +141,7 @@ export function ReservesPage() {
                     {c.condition_rating}/10
                   </Badge>
                 </Table.Td>
-                <Table.Td><ActionIcon variant="subtle" onClick={() => handleEdit(c)}><IconEdit size={16} /></ActionIcon></Table.Td>
+                <Table.Td>{!isReadOnly && <ActionIcon variant="subtle" onClick={() => handleEdit(c)}><IconEdit size={16} /></ActionIcon>}</Table.Td>
               </Table.Tr>
             );
           })}