fix(plugin): add GET and PATCH /api/v1/plugins/{name}/config endpoints

Bug 4: Plugin config field existed but had no API endpoints. Added
GET /api/v1/plugins/{name}/config to retrieve config as JSON and
PATCH /api/v1/plugins/{name}/config to update it. Uses PluginConfigUpdate
Pydantic model for request validation.

app/routes/plugins.py

@@ -1,8 +1,9 @@
-"""Plugin routes — list, install, activate, deactivate, uninstall, manifest schema."""
+"""Plugin routes — list, install, activate, deactivate, uninstall, manifest schema, config."""
 
 from __future__ import annotations
 
 from fastapi import APIRouter, Depends, HTTPException, Query
+from pydantic import BaseModel
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.db import get_db
@@ -13,6 +14,11 @@ from app.services.plugin_service import get_plugin_service
 router = APIRouter(prefix="/api/v1/plugins", tags=["plugins"])
 
 
+class PluginConfigUpdate(BaseModel):
+    """Request body for updating plugin configuration."""
+    config: dict
+
+
 @router.get("")
 async def list_plugins(
     db: AsyncSession = Depends(get_db),
@@ -33,6 +39,55 @@ async def get_manifest_schema(
     return service.get_manifest_schema()
 
 
+@router.get("/{name}/config")
+async def get_plugin_config(
+    name: str,
+    db: AsyncSession = Depends(get_db),
+    current_user: dict = Depends(require_admin),
+):
+    """Get the configuration for a specific plugin.
+
+    Returns the plugin's config field as a JSON object.
+    """
+    service = get_plugin_service()
+    try:
+        config = await service.get_plugin_config(db, name)
+        return {"name": name, "config": config}
+    except ValueError as exc:
+        raise HTTPException(
+            404, detail={"detail": str(exc), "code": "plugin_not_found"}
+        ) from None
+
+
+@router.patch("/{name}/config")
+async def update_plugin_config(
+    name: str,
+    body: PluginConfigUpdate,
+    db: AsyncSession = Depends(get_db),
+    current_user: dict = Depends(require_admin),
+):
+    """Update the configuration for a specific plugin.
+
+    Stores the config as a JSON string in the plugin's config field.
+    """
+    import uuid as uuid_mod
+
+    service = get_plugin_service()
+    try:
+        result = await service.update_plugin_config(
+            db,
+            name,
+            config=body.config,
+            tenant_id=uuid_mod.UUID(current_user["tenant_id"]),
+            user_id=uuid_mod.UUID(current_user["user_id"]),
+        )
+        return result
+    except ValueError as exc:
+        raise HTTPException(
+            404, detail={"detail": str(exc), "code": "plugin_not_found"}
+        ) from None
+
+
 @router.post("/{name}/install")
 async def install_plugin(
     name: str,