feat: wire frontend pages to live APIs and standardize response contracts (P1)

- Backend: Add COUNT query and paginated response shape to conversations endpoint
  Returns { conversations: [...], total, page, per_page } instead of flat array
- Frontend: Replace mock data in DashboardPage with fetchAnalytics() API calls
- Frontend: Replace mock data in ReplayListPage with fetchConversations() API calls
- Frontend: Replace mock data in ReplayPage with fetchReplay() API calls
- Add proper loading, empty, and error states to all three pages
- Align ConversationSummary type with actual DB columns (created_at, status)
- Update unit and E2E tests for new paginated conversation response shape
- Add fetchone() to FakeCursor for COUNT query support in E2E tests

backend/tests/unit/replay/test_api.py

@@ -19,13 +19,35 @@ def _build_app() -> FastAPI:
     return app
 
 
-def _make_mock_pool(fetchall_result: list[dict]) -> MagicMock:
-    """Build a mock pool that returns the given rows from fetchall."""
-    mock_cursor = AsyncMock()
-    mock_cursor.fetchall = AsyncMock(return_value=fetchall_result)
+def _make_mock_pool(
+    fetchall_result: list[dict],
+    *,
+    count: int | None = None,
+) -> MagicMock:
+    """Build a mock pool that returns the given rows from fetchall.
 
-    mock_conn = AsyncMock()
-    mock_conn.execute = AsyncMock(return_value=mock_cursor)
+    When *count* is provided, the first execute() call returns a cursor
+    whose fetchone() yields ``(count,)`` (for the COUNT query) and the
+    second call returns the rows via fetchall().  When *count* is None
+    (the default), a single cursor backed by *fetchall_result* is used
+    for all calls.
+    """
+    if count is not None:
+        count_cursor = AsyncMock()
+        count_cursor.fetchone = AsyncMock(return_value=(count,))
+
+        rows_cursor = AsyncMock()
+        rows_cursor.fetchall = AsyncMock(return_value=fetchall_result)
+
+        mock_conn = AsyncMock()
+        mock_conn.execute = AsyncMock(side_effect=[count_cursor, rows_cursor])
+    else:
+        mock_cursor = AsyncMock()
+        mock_cursor.fetchall = AsyncMock(return_value=fetchall_result)
+        mock_cursor.fetchone = AsyncMock(return_value=None)
+
+        mock_conn = AsyncMock()
+        mock_conn.execute = AsyncMock(return_value=mock_cursor)
 
     mock_ctx = AsyncMock()
     mock_ctx.__aenter__ = AsyncMock(return_value=mock_conn)
@@ -39,14 +61,17 @@ def _make_mock_pool(fetchall_result: list[dict]) -> MagicMock:
 class TestListConversations:
     def test_returns_200_with_empty_list(self) -> None:
         app = _build_app()
-        app.state.pool = _make_mock_pool([])
+        app.state.pool = _make_mock_pool([], count=0)
 
         with TestClient(app) as client:
             resp = client.get("/api/conversations")
         assert resp.status_code == 200
         body = resp.json()
         assert body["success"] is True
-        assert isinstance(body["data"], list)
+        data = body["data"]
+        assert isinstance(data["conversations"], list)
+        assert data["total"] == 0
+        assert data["page"] == 1
         assert body["error"] is None
 
     def test_returns_conversations_list(self) -> None:
@@ -61,18 +86,20 @@ class TestListConversations:
                 "total_cost_usd": 0.01,
             }
         ]
-        app.state.pool = _make_mock_pool(mock_rows)
+        app.state.pool = _make_mock_pool(mock_rows, count=1)
 
         with TestClient(app) as client:
             resp = client.get("/api/conversations")
         body = resp.json()
         assert resp.status_code == 200
-        assert len(body["data"]) == 1
-        assert body["data"][0]["thread_id"] == "t1"
+        data = body["data"]
+        assert len(data["conversations"]) == 1
+        assert data["conversations"][0]["thread_id"] == "t1"
+        assert data["total"] == 1
 
     def test_pagination_defaults(self) -> None:
         app = _build_app()
-        app.state.pool = _make_mock_pool([])
+        app.state.pool = _make_mock_pool([], count=0)
 
         with TestClient(app) as client:
             resp = client.get("/api/conversations")
@@ -80,7 +107,7 @@ class TestListConversations:
 
     def test_pagination_custom_params(self) -> None:
         app = _build_app()
-        app.state.pool = _make_mock_pool([])
+        app.state.pool = _make_mock_pool([], count=0)
 
         with TestClient(app) as client:
             resp = client.get("/api/conversations?page=2&per_page=10")
@@ -88,7 +115,7 @@ class TestListConversations:
 
     def test_per_page_max_capped_at_100(self) -> None:
         app = _build_app()
-        app.state.pool = _make_mock_pool([])
+        app.state.pool = _make_mock_pool([], count=0)
 
         with TestClient(app) as client:
             resp = client.get("/api/conversations?per_page=200")