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/schemas/schemas.py

@@ -264,32 +264,32 @@ class MilestoneResponse(MilestoneBase):
         from_attributes = True
 
 
-# Propose schemas
+# Proposal schemas (renamed from Propose)
 
-class ProposeStatusEnum(str, Enum):
+class ProposalStatusEnum(str, Enum):
     OPEN = "open"
     ACCEPTED = "accepted"
     REJECTED = "rejected"
 
 
-class ProposeBase(BaseModel):
+class ProposalBase(BaseModel):
     title: str
     description: Optional[str] = None
 
 
-class ProposeCreate(ProposeBase):
+class ProposalCreate(ProposalBase):
     project_id: Optional[int] = None
 
 
-class ProposeUpdate(BaseModel):
+class ProposalUpdate(BaseModel):
     title: Optional[str] = None
     description: Optional[str] = None
 
 
-class ProposeResponse(ProposeBase):
+class ProposalResponse(ProposalBase):
     id: int
-    propose_code: Optional[str] = None
-    status: ProposeStatusEnum
+    propose_code: Optional[str] = None  # DB column name kept for compat
+    status: ProposalStatusEnum
     project_id: int
     created_by_id: Optional[int] = None
     created_by_username: Optional[str] = None
@@ -301,6 +301,14 @@ class ProposeResponse(ProposeBase):
         from_attributes = True
 
 
+# Backward-compatible aliases
+ProposeStatusEnum = ProposalStatusEnum
+ProposeBase = ProposalBase
+ProposeCreate = ProposalCreate
+ProposeUpdate = ProposalUpdate
+ProposeResponse = ProposalResponse
+
+
 # Paginated response
 from typing import Generic, TypeVar
 T = TypeVar("T")