feat(phase-39): role-based access control overhaul + forced password change

- Add must_change_password field to User model with migration b023

- Add POST /auth/change-password endpoint with password policy validation

- Add require_password_changed dependency to block requests until password is changed

- Add ChangePasswordModal with live password policy checklist (forced on first login)

- Show password policy in CreateUserModal and EditUserModal

- Fix backend permissions: tests, campaigns, templates, reports, evidence, worklogs

- red_tech/blue_tech: execute only, cannot create tests/campaigns/templates

- red_lead/blue_lead: create/edit tests/campaigns/templates, generate reports, no system access

- viewer: read-only everywhere, can generate reports

- Fix frontend role checks across TestDetailPage, TestDetailHeader, TeamTabs, TestsPage, CampaignsPage, CampaignDetailPage, Sidebar

backend/app/models/user.py

@@ -27,5 +27,6 @@ class User(Base):
     hashed_password = Column(String, nullable=False)
     role = Column(String, nullable=False, default="viewer")
     is_active = Column(Boolean, default=True)
+    must_change_password = Column(Boolean, default=True)
     created_at = Column(DateTime, default=datetime.utcnow)
     last_login = Column(DateTime, nullable=True)