feat(cma): treasury stage-1 MVP - migration, models, endpoints, rules, 2 pages

G1 review fixes P0-1/P0-2/P1-3/P1-4/P1-5/P2-6/P2-7/P2-8 applied:
- up() filters comment lines then asserts missing_tables == [] (CREATE hits 6/6)
- created counter = new-object diff via information_schema (idempotent second run = 0)
- down() drops columns per-column, dumps via write-path creds + fail-closed
- seeds expanded to 8 rules + 6 limits; data_status DEFAULT estimated
- no physical FK (app-layer checks), amount FLOAT wan-yuan, round(x,4)

Scope: 6 treasury_* tables + cash_plans 4 added columns; cash.py untouched.
Not pushed: deploy is approval-gated (de851257).

backend/app/models/__init__.py

@@ -8,6 +8,10 @@ from app.models.knowledge import KnowledgeEvent, KnowledgeSummary
 from app.models.driver_budget import DriverFactorTemplate, DriverFactorBudget
 from app.models.product_sales import ProductSales
 from app.models.ext_input_ledger import TaxFilingLog, HrMonthlyLedger, LicenceLedger
+from app.models.treasury import (
+    TreasuryAccount, TreasuryBalance, TreasuryControlRule,
+    TreasuryPayment, TreasuryControlHit, TreasuryLimit,
+)
 
 
 class Entity(Base):