Refactor cycle update and delete tests

### Description
This pull request resolves [Issue #170](#170) by consolidating the fragmented and duplicated `TestUpdateCycle` and `TestDeleteCycle` classes in `backend/tests/test_cycles.py`.

#### Details:
* **Class Consolidation:** Merged all test methods for updating and deleting cycles into single, unified `TestUpdateCycle` and `TestDeleteCycle` classes respectively.
* **Removal of Duplicates:** Eliminated duplicate `not_found` test definitions that resulted from the fragmented class structure.
* **Pipeline Integrity:** Ensures success tests (`test_update_cycle_success` and `test_delete_cycle_success`) are no longer shadowed and are fully executed during test runs.

Closes #170

Author: mspandey

backend/tests/test_cycles.py

@@ -151,9 +151,17 @@ def test_update_cycle_success(self, client, auth_headers):
 
     def test_update_cycle_not_found(self, client, auth_headers):
         """Non-existent cycle returns 404."""
-        resp = client.put("/cycles/bad_id", headers=auth_headers, json={"startDate": "2026-06-01", "endDate": "2026-06-05"})
+        resp = client.put("/cycles/nonexistent_id", headers=auth_headers, json={"startDate": "2026-07-01"})
         assert resp.status_code == 404
 
+    def test_update_cycle_invalid_dates(self, client, auth_headers):
+        """Updating with invalid date range returns 400."""
+        resp = client.put("/cycles/some_id", headers=auth_headers, json={
+            "startDate": "2026-07-10",
+            "endDate": "2026-07-05",
+        })
+        assert resp.status_code == 400 or resp.status_code == 404
+
 
 class TestDeleteCycle:
     """DELETE /cycles/<id> endpoint tests."""
@@ -171,9 +179,14 @@ def test_delete_cycle_success(self, client, auth_headers):
 
     def test_delete_cycle_not_found(self, client, auth_headers):
         """Non-existent cycle returns 404."""
-        resp = client.delete("/cycles/bad_id", headers=auth_headers)
+        resp = client.delete("/cycles/nonexistent_id", headers=auth_headers)
         assert resp.status_code == 404
 
+    def test_delete_cycle_no_auth(self, client):
+        """Deleting without auth returns 401."""
+        resp = client.delete("/cycles/some_id")
+        assert resp.status_code == 401
+
 
 class TestCyclePrediction:
     """GET /cycle-prediction endpoint tests."""
@@ -185,34 +198,3 @@ def test_cycle_prediction_success(self, client, auth_headers):
         assert resp.status_code == 200
         data = resp.get_json()
         assert isinstance(data, dict)
-
-
-class TestUpdateCycle:
-    """PUT /cycles/<id> endpoint tests."""
-
-    def test_update_cycle_not_found(self, client, auth_headers):
-        """Updating a non-existent cycle returns 404."""
-        resp = client.put("/cycles/nonexistent_id", headers=auth_headers, json={"startDate": "2026-07-01"})
-        assert resp.status_code == 404
-
-    def test_update_cycle_invalid_dates(self, client, auth_headers):
-        """Updating with invalid date range returns 400."""
-        resp = client.put("/cycles/some_id", headers=auth_headers, json={
-            "startDate": "2026-07-10",
-            "endDate": "2026-07-05",
-        })
-        assert resp.status_code == 400 or resp.status_code == 404
-
-
-class TestDeleteCycle:
-    """DELETE /cycles/<id> endpoint tests."""
-
-    def test_delete_cycle_not_found(self, client, auth_headers):
-        """Deleting a non-existent cycle returns 404."""
-        resp = client.delete("/cycles/nonexistent_id", headers=auth_headers)
-        assert resp.status_code == 404
-
-    def test_delete_cycle_no_auth(self, client):
-        """Deleting without auth returns 401."""
-        resp = client.delete("/cycles/some_id")
-        assert resp.status_code == 401