BE-PR-001: Rename Propose -> Proposal across backend

- New canonical model: Proposal, ProposalStatus (app/models/proposal.py)
- New canonical router: /projects/{id}/proposals (app/api/routers/proposals.py)
- Schemas renamed: ProposalCreate, ProposalUpdate, ProposalResponse, etc.
- Old propose.py and proposes.py kept as backward-compat shims
- Legacy /proposes API still works (delegates to /proposals handlers)
- DB table name (proposes), column (propose_code), and permission names
  (propose.*) kept unchanged for zero-migration compat
- Updated init_wizard.py comments

app/main.py

@@ -57,7 +57,8 @@ from app.api.routers.misc import router as misc_router
 from app.api.routers.monitor import router as monitor_router
 from app.api.routers.milestones import router as milestones_router
 from app.api.routers.roles import router as roles_router
-from app.api.routers.proposes import router as proposes_router
+from app.api.routers.proposals import router as proposals_router
+from app.api.routers.proposes import router as proposes_router  # legacy compat
 from app.api.routers.milestone_actions import router as milestone_actions_router
 from app.api.routers.meetings import router as meetings_router
 
@@ -71,7 +72,8 @@ app.include_router(misc_router)
 app.include_router(monitor_router)
 app.include_router(milestones_router)
 app.include_router(roles_router)
-app.include_router(proposes_router)
+app.include_router(proposals_router)
+app.include_router(proposes_router)  # legacy compat
 app.include_router(milestone_actions_router)
 app.include_router(meetings_router)
 
@@ -291,7 +293,7 @@ def _sync_default_user_roles(db):
 @app.on_event("startup")
 def startup():
     from app.core.config import Base, engine, SessionLocal
-    from app.models import models, webhook, apikey, activity, milestone, notification, worklog, monitor, role_permission, task, support, meeting, propose
+    from app.models import models, webhook, apikey, activity, milestone, notification, worklog, monitor, role_permission, task, support, meeting, proposal, propose
     Base.metadata.create_all(bind=engine)
     _migrate_schema()