feat: add Board Planning module with investment/assessment scenario modeling

Implements Phase 11 Forecasting Tools - a "what-if" scenario planning system
for HOA boards to model financial decisions before committing.

Backend:
- 3 new tenant-scoped tables: board_scenarios, scenario_investments, scenario_assessments
- Migration script (013) for existing tenants
- Full CRUD service for scenarios, investments, and assessments
- Projection engine adapted from cash flow forecast with investment/assessment deltas
- Scenario comparison endpoint (up to 4 scenarios)
- Investment execution flow: converts planned → real investment_accounts + journal entry

Frontend:
- New "Board Planning" sidebar section with 3 pages
- Investment Scenarios: list, create, detail with investments table + timeline
- Assessment Scenarios: list, create, detail with changes table
- Scenario Comparison: multi-select overlay chart + summary metrics
- Shared components: ProjectionChart, InvestmentTimeline, ScenarioCard, forms
- AI Recommendation → Investment Plan integration (Story 1A)

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

frontend/src/pages/board-planning/InvestmentScenariosPage.tsx

@@ -0,0 +1,128 @@
+import { useState } from 'react';
+import { Title, Text, Stack, Group, Button, SimpleGrid, Modal, TextInput, Textarea, Loader, Center } from '@mantine/core';
+import { IconPlus } from '@tabler/icons-react';
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { useNavigate } from 'react-router-dom';
+import { notifications } from '@mantine/notifications';
+import api from '../../services/api';
+import { ScenarioCard } from './components/ScenarioCard';
+
+export function InvestmentScenariosPage() {
+  const navigate = useNavigate();
+  const queryClient = useQueryClient();
+  const [createOpen, setCreateOpen] = useState(false);
+  const [editScenario, setEditScenario] = useState<any>(null);
+  const [form, setForm] = useState({ name: '', description: '' });
+
+  const { data: scenarios, isLoading } = useQuery<any[]>({
+    queryKey: ['board-planning-scenarios', 'investment'],
+    queryFn: async () => {
+      const { data } = await api.get('/board-planning/scenarios?type=investment');
+      return data;
+    },
+  });
+
+  const createMutation = useMutation({
+    mutationFn: (dto: any) => api.post('/board-planning/scenarios', dto),
+    onSuccess: (res) => {
+      queryClient.invalidateQueries({ queryKey: ['board-planning-scenarios'] });
+      setCreateOpen(false);
+      setForm({ name: '', description: '' });
+      notifications.show({ message: 'Scenario created', color: 'green' });
+      navigate(`/board-planning/investments/${res.data.id}`);
+    },
+  });
+
+  const updateMutation = useMutation({
+    mutationFn: ({ id, ...dto }: any) => api.put(`/board-planning/scenarios/${id}`, dto),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['board-planning-scenarios'] });
+      setEditScenario(null);
+      notifications.show({ message: 'Scenario updated', color: 'green' });
+    },
+  });
+
+  const deleteMutation = useMutation({
+    mutationFn: (id: string) => api.delete(`/board-planning/scenarios/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['board-planning-scenarios'] });
+      notifications.show({ message: 'Scenario archived', color: 'orange' });
+    },
+  });
+
+  if (isLoading) return <Center h={400}><Loader size="lg" /></Center>;
+
+  return (
+    <Stack>
+      <Group justify="space-between" align="flex-start">
+        <div>
+          <Title order={2}>Investment Scenarios</Title>
+          <Text c="dimmed" size="sm">
+            Model different investment strategies and compare their impact on liquidity and income
+          </Text>
+        </div>
+        <Button leftSection={<IconPlus size={16} />} onClick={() => setCreateOpen(true)}>
+          New Scenario
+        </Button>
+      </Group>
+
+      {scenarios && scenarios.length > 0 ? (
+        <SimpleGrid cols={{ base: 1, sm: 2, lg: 3 }}>
+          {scenarios.map((s) => (
+            <ScenarioCard
+              key={s.id}
+              scenario={s}
+              onClick={() => navigate(`/board-planning/investments/${s.id}`)}
+              onEdit={() => { setEditScenario(s); setForm({ name: s.name, description: s.description || '' }); }}
+              onDelete={() => deleteMutation.mutate(s.id)}
+            />
+          ))}
+        </SimpleGrid>
+      ) : (
+        <Center py="xl">
+          <Stack align="center" gap="sm">
+            <Text c="dimmed">No investment scenarios yet</Text>
+            <Text size="sm" c="dimmed" maw={400} ta="center">
+              Create a scenario to model investment allocations, timing, and their impact on reserves and liquidity.
+            </Text>
+          </Stack>
+        </Center>
+      )}
+
+      {/* Create Modal */}
+      <Modal opened={createOpen} onClose={() => setCreateOpen(false)} title="New Investment Scenario">
+        <Stack>
+          <TextInput label="Name" required value={form.name} onChange={(e) => setForm({ ...form, name: e.target.value })} placeholder="e.g. Conservative CD Ladder" />
+          <Textarea label="Description" value={form.description} onChange={(e) => setForm({ ...form, description: e.target.value })} placeholder="Describe this investment strategy..." />
+          <Group justify="flex-end">
+            <Button variant="default" onClick={() => setCreateOpen(false)}>Cancel</Button>
+            <Button
+              onClick={() => createMutation.mutate({ name: form.name, description: form.description, scenarioType: 'investment' })}
+              loading={createMutation.isPending}
+              disabled={!form.name}
+            >
+              Create Scenario
+            </Button>
+          </Group>
+        </Stack>
+      </Modal>
+
+      {/* Edit Modal */}
+      <Modal opened={!!editScenario} onClose={() => setEditScenario(null)} title="Edit Scenario">
+        <Stack>
+          <TextInput label="Name" required value={form.name} onChange={(e) => setForm({ ...form, name: e.target.value })} />
+          <Textarea label="Description" value={form.description} onChange={(e) => setForm({ ...form, description: e.target.value })} />
+          <Group justify="flex-end">
+            <Button variant="default" onClick={() => setEditScenario(null)}>Cancel</Button>
+            <Button
+              onClick={() => updateMutation.mutate({ id: editScenario.id, name: form.name, description: form.description })}
+              loading={updateMutation.isPending}
+            >
+              Save Changes
+            </Button>
+          </Group>
+        </Stack>
+      </Modal>
+    </Stack>
+  );
+}