0.2.46: security hardening (external-fund scope, role guards, forced password rotation, headers)

Pre-release audit fixes:
- External Administrators can only act on investors already in their own funds
  (grant_access, create_statement, set_partner_exited, import match), closing a
  cross-fund account-takeover chain.
- Role and is_active changes are gated: no self-escalation, non-approvers cannot
  mint or alter approver accounts, and the Service Admin is protected.
- must_change_password is enforced server-side, not just in the client.
- Session cookie is Secure with a 12h max-age and SameSite; CSP and standard
  security headers on every response; the app refuses to boot on a known or short
  session secret; uvicorn runs with proxy-headers so login throttling keys on the
  real client IP behind the platform proxy.
- Import preview no longer confirms cross-fund investors; no-store on document
  downloads.
- Adds backend/tests/test_security_hardening.py (15 tests); full suite 76 passing.
- SECURITY-AUDIT.md records the swarm audit, findings, and remediation status.

deploy/startos/install/versions/v_0_2_46.ts

@@ -0,0 +1,19 @@
+import { VersionInfo } from '@start9labs/start-sdk'
+
+export const v_0_2_46 = VersionInfo.of({
+  version: '0.2.46:0',
+  releaseNotes: {
+    en_US:
+      'Security hardening ahead of the investor release. External Administrators can now only ' +
+      'act on investors already in their own funds (closing a cross-fund account-takeover path). ' +
+      'Role and active-status changes are restricted so staff cannot escalate their own ' +
+      'permissions or alter the Service Admin. The forced first-login password change is now ' +
+      'enforced by the server, not just the browser. Session cookies are marked Secure with a ' +
+      'shorter lifetime, standard security headers are set on every response, and login ' +
+      'throttling now sees the real client address behind the platform proxy.',
+  },
+  migrations: {
+    up: async ({ effects }) => {},
+    down: async ({ effects }) => {},
+  },
+})