feat: add nowcast point alarm unregister client with confirmation and backup

Shows environment, count and an irreversibility warning, requires typing the confirmation word (plus the environment name on prod), backs every registration up through get-by-id before deleting and aborts the whole run if the backup cannot be completed.

tests/test_point_alarm.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import csv
+import io
 import json
 import os
 import tempfile
@@ -15,6 +16,7 @@ from common import ApiError, ConfigurationError
 from common.client import ApiResponse
 from point_alarm import (
     PointRegistrationProcessor,
+    PointUnregisterProcessor,
     PointUpdateProcessor,
     build_update_payload,
     PointStore,
@@ -294,5 +296,48 @@ class UpdateTest(unittest.TestCase):
             self.assertEqual((row["status"], row["httpStatus"]), ("SUCCESS", "HTTP_200"))
 
 
+class UnregisterTest(unittest.TestCase):
+    class Svc:
+        def __init__(self) -> None:
+            self.deleted: list[str] = []
+
+        def get_by_id(self, value):
+            return ApiResponse(200, dict(registration(1), registrationId=value))
+
+        def unregister(self, value):
+            self.deleted.append(value)
+            return ApiResponse(204, None)
+
+    def make(self, svc, answers, env="test", backup=None):
+        queue = list(answers)
+        return PointUnregisterProcessor(
+            svc, ids=[REG_ID], environment=env, base_url="https://x",
+            backup_path=backup, input_fn=lambda _: queue.pop(0), out=io.StringIO(),
+        )
+
+    def test_wrong_confirmation_deletes_nothing(self) -> None:
+        svc = self.Svc()
+        self.assertEqual(self.make(svc, ["sil"]).run(), [])
+        self.assertEqual(svc.deleted, [])
+
+    def test_prod_needs_environment_name(self) -> None:
+        svc = self.Svc()
+        self.assertEqual(self.make(svc, ["test"], env="prod").run(), [])
+        self.assertEqual(svc.deleted, [])
+        self.assertEqual(len(self.make(svc, ["prod", "SİL"], env="prod").run()), 1)
+
+    def test_backup_written_before_delete_and_failure_blocks(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            svc = self.Svc()
+            backup = Path(tmp) / "b.csv"
+            results = self.make(svc, ["SİL"], backup=backup).run()
+            self.assertEqual(results[0]["status"], "SUCCESS")
+            self.assertIn(REG_ID, backup.read_text(encoding="utf-8-sig"))
+            svc2 = self.Svc()
+            with self.assertRaises(OSError):
+                self.make(svc2, ["SİL"], backup=Path(tmp) / "no" / "b.csv").run()
+            self.assertEqual(svc2.deleted, [])
+
+
 if __name__ == "__main__":
     unittest.main()