fix: use ASGITransport for httpx AsyncClient in tests

- httpx.AsyncClient requires ASGITransport for FastAPI app testing
- Updated all test files to use correct API

backend/tests/test_sources.py

@@ -1,10 +1,10 @@
 import pytest
-from httpx import AsyncClient
+from httpx import AsyncClient, ASGITransport
 from app.main import app
 
 @pytest.mark.asyncio
 async def test_create_source():
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         response = await ac.post("/api/sources/", json={
             "name": "Test Source",
             "type": "local",
@@ -18,7 +18,7 @@ async def test_create_source():
 
 @pytest.mark.asyncio
 async def test_list_sources():
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         # Create source first
         await ac.post("/api/sources/", json={
             "name": "Test Source",
@@ -33,7 +33,7 @@ async def test_list_sources():
 
 @pytest.mark.asyncio
 async def test_get_source():
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         create_resp = await ac.post("/api/sources/", json={
             "name": "Test Source",
             "type": "local",
@@ -47,7 +47,7 @@ async def test_get_source():
 
 @pytest.mark.asyncio
 async def test_delete_source():
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         create_resp = await ac.post("/api/sources/", json={
             "name": "Delete Me",
             "type": "local",
@@ -59,13 +59,13 @@ async def test_delete_source():
     assert response.status_code == 200
     
     # Verify deletion
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         get_resp = await ac.get(f"/api/sources/{source_id}")
     assert get_resp.status_code == 404
 
 @pytest.mark.asyncio
 async def test_update_source():
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         create_resp = await ac.post("/api/sources/", json={
             "name": "Original Name",
             "type": "local",
@@ -82,18 +82,18 @@ async def test_update_source():
 
 @pytest.mark.asyncio
 async def test_get_source_not_found():
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         response = await ac.get("/api/sources/99999")
     assert response.status_code == 404
 
 @pytest.mark.asyncio
 async def test_update_source_not_found():
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         response = await ac.put("/api/sources/99999", json={"name": "Test"})
     assert response.status_code == 404
 
 @pytest.mark.asyncio
 async def test_delete_source_not_found():
-    async with AsyncClient(app=app, base_url="http://test") as ac:
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as ac:
         response = await ac.delete("/api/sources/99999")
     assert response.status_code == 404