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>

backend/src/database/tenant-schema.service.ts

@@ -366,6 +366,64 @@ export class TenantSchemaService {
         created_at TIMESTAMPTZ DEFAULT NOW()
       )`,
 
+      // Board Planning - Scenarios
+      `CREATE TABLE "${s}".board_scenarios (
+        id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+        name VARCHAR(255) NOT NULL,
+        description TEXT,
+        scenario_type VARCHAR(30) NOT NULL CHECK (scenario_type IN ('investment', 'assessment')),
+        status VARCHAR(20) DEFAULT 'draft' CHECK (status IN ('draft', 'active', 'approved', 'archived')),
+        projection_months INTEGER DEFAULT 36,
+        projection_cache JSONB,
+        projection_cached_at TIMESTAMPTZ,
+        created_by UUID NOT NULL,
+        created_at TIMESTAMPTZ DEFAULT NOW(),
+        updated_at TIMESTAMPTZ DEFAULT NOW()
+      )`,
+
+      // Board Planning - Scenario Investments
+      `CREATE TABLE "${s}".scenario_investments (
+        id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+        scenario_id UUID NOT NULL REFERENCES "${s}".board_scenarios(id) ON DELETE CASCADE,
+        source_recommendation_id UUID,
+        label VARCHAR(255) NOT NULL,
+        investment_type VARCHAR(50) CHECK (investment_type IN ('cd', 'money_market', 'treasury', 'savings', 'other')),
+        fund_type VARCHAR(20) NOT NULL CHECK (fund_type IN ('operating', 'reserve')),
+        principal DECIMAL(15,2) NOT NULL,
+        interest_rate DECIMAL(6,4),
+        term_months INTEGER,
+        institution VARCHAR(255),
+        purchase_date DATE,
+        maturity_date DATE,
+        auto_renew BOOLEAN DEFAULT FALSE,
+        executed_investment_id UUID,
+        notes TEXT,
+        sort_order INTEGER DEFAULT 0,
+        created_at TIMESTAMPTZ DEFAULT NOW(),
+        updated_at TIMESTAMPTZ DEFAULT NOW()
+      )`,
+
+      // Board Planning - Scenario Assessments
+      `CREATE TABLE "${s}".scenario_assessments (
+        id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+        scenario_id UUID NOT NULL REFERENCES "${s}".board_scenarios(id) ON DELETE CASCADE,
+        change_type VARCHAR(30) NOT NULL CHECK (change_type IN ('dues_increase', 'special_assessment', 'dues_decrease')),
+        label VARCHAR(255) NOT NULL,
+        target_fund VARCHAR(20) CHECK (target_fund IN ('operating', 'reserve', 'both')),
+        percentage_change DECIMAL(6,3),
+        flat_amount_change DECIMAL(10,2),
+        special_total DECIMAL(15,2),
+        special_per_unit DECIMAL(10,2),
+        special_installments INTEGER DEFAULT 1,
+        effective_date DATE NOT NULL,
+        end_date DATE,
+        applies_to_group_id UUID,
+        notes TEXT,
+        sort_order INTEGER DEFAULT 0,
+        created_at TIMESTAMPTZ DEFAULT NOW(),
+        updated_at TIMESTAMPTZ DEFAULT NOW()
+      )`,
+
       // Indexes
       `CREATE INDEX "idx_${s}_att_je" ON "${s}".attachments(journal_entry_id)`,
       `CREATE INDEX "idx_${s}_je_date" ON "${s}".journal_entries(entry_date)`,
@@ -378,6 +436,9 @@ export class TenantSchemaService {
       `CREATE INDEX "idx_${s}_pay_unit" ON "${s}".payments(unit_id)`,
       `CREATE INDEX "idx_${s}_pay_inv" ON "${s}".payments(invoice_id)`,
       `CREATE INDEX "idx_${s}_bud_year" ON "${s}".budgets(fiscal_year)`,
+      `CREATE INDEX "idx_${s}_bs_type_status" ON "${s}".board_scenarios(scenario_type, status)`,
+      `CREATE INDEX "idx_${s}_si_scenario" ON "${s}".scenario_investments(scenario_id)`,
+      `CREATE INDEX "idx_${s}_sa_scenario" ON "${s}".scenario_assessments(scenario_id)`,
     ];
   }