fix: accept tool instance creation params in request body

The create_instance endpoint was expecting tool_type_id and display_name
as query parameters, but the frontend sends them in the JSON body.
Added CreateInstanceRequest Pydantic model to properly parse the request body.

Fixes 422 Unprocessable Content error on instance creation.

apps/api/src/api/tool_instances.py

@@ -5,6 +5,7 @@ import uuid
 from datetime import datetime
 
 from fastapi import APIRouter, Depends, HTTPException, status
+from pydantic import BaseModel, Field
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -29,6 +30,13 @@ from src.services.docker import (
 router = APIRouter(prefix="/projects", tags=["tool-instances"])
 
 
+class CreateInstanceRequest(BaseModel):
+    """Request body for creating a tool instance."""
+
+    tool_type_id: str = Field(description="UUID of the tool type to instantiate")
+    display_name: str | None = Field(default=None, description="Optional display name for the instance")
+
+
 async def _get_user(session: AsyncSession, user_id: uuid.UUID) -> User:
     """Fetch a user by ID or raise 404 if not found."""
     user = await session.get(User, user_id)
@@ -71,8 +79,7 @@ async def _get_owned_project(
 async def create_instance(
     project_id: uuid.UUID,
     repo_id: uuid.UUID,
-    tool_type_id: uuid.UUID,
-    display_name: str | None = None,
+    data: CreateInstanceRequest,
     user_id: uuid.UUID = Depends(get_current_user_id),
     session: AsyncSession = Depends(get_db_session),
 ) -> dict:
@@ -98,6 +105,7 @@ async def create_instance(
             status_code=status.HTTP_404_NOT_FOUND, detail="repository not found"
         )
 
+    tool_type_id = uuid.UUID(data.tool_type_id)
     tool_type = await session.get(ToolType, tool_type_id)
     if tool_type is None:
         raise HTTPException(
@@ -106,7 +114,7 @@ async def create_instance(
 
     # Generate unique name
     instance_name = f"{tool_type.name}-{repo.name}-{uuid.uuid4().hex[:8]}"
-    instance_display = display_name or f"{tool_type.display_name} - {repo.name}"
+    instance_display = data.display_name or f"{tool_type.display_name} - {repo.name}"
 
     # Create instance directory
     instance_dir = ensure_instance_directory(instance_name)