feat: allow updating existing CV branches

apps/backend/fastapi/app/api/routes/versions.py

@@ -4,8 +4,12 @@ from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.api.deps import get_current_user, get_db
-from app.schemas import BranchCreateRequest, VersionResponse
-from app.services.versions import create_branch, delete_version
+from app.schemas import BranchCreateRequest, PatchApplyRequest, VersionResponse
+from app.services.versions import (
+    append_patches_to_version,
+    create_branch,
+    delete_version,
+)
 from dlib.auth import AuthenticatedUser
 from dlib.cv.ats_guard import PatchValidationError
 
@@ -48,3 +52,26 @@ async def delete_version_branch(
         raise HTTPException(status_code=400, detail="Cannot delete root version")
     if result == "has_children":
         raise HTTPException(status_code=409, detail="Delete child branches first")
+
+
+@router.post("/{version_id}/patches", response_model=VersionResponse)
+async def append_patches(
+    version_id: str,
+    payload: PatchApplyRequest,
+    session: AsyncSession = Depends(get_db),
+    user: AuthenticatedUser = Depends(get_current_user),
+):
+    if not payload.patches:
+        raise HTTPException(status_code=400, detail="No patches provided")
+    try:
+        version = await append_patches_to_version(
+            session,
+            owner_id=user.sub,
+            version_id=version_id,
+            patches=payload.patches,
+        )
+    except PatchValidationError as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
+    if not version:
+        raise HTTPException(status_code=404, detail="Version not found")
+    return VersionResponse.model_validate(version)