fix: workspace creation SSH authentication

- GitService.clone() now accepts ssh_key and sets up GIT_SSH_COMMAND env
- WorkspaceManager.create() loads repo SSH key from DB and decrypts it
- Both workspace create endpoints pass session for SSH key lookup

Quality gates: ruff clean, pytest workspaces API (9 passed, 1 skipped)

apps/api/src/api/workspaces.py

@@ -95,7 +95,7 @@ async def create_workspace_top_level(
 
     manager = WorkspaceManager()
     try:
-        workspace = await manager.create(repo, user_id, name, branch)
+        workspace = await manager.create(repo, user_id, name, branch, session=session)
         session.add(workspace)
         await session.commit()
     except Exception as exc:
@@ -191,7 +191,7 @@ async def create_workspace(
 
     manager = WorkspaceManager()
     try:
-        workspace = await manager.create(repo, user_id, name, branch)
+        workspace = await manager.create(repo, user_id, name, branch, session=session)
         session.add(workspace)
         await session.commit()
     except Exception as exc: