Add route management web interface

Prompts used since previous commit:
- Kun je ook een webinterface maken waarmee ik de regels kan beheren?
- Ik wil dat de webinterface benaderbaar is vanaf mijn hele interne netwerk. En ik wil alle regels kunnen beheren. Dus ook de bestaande ingebouwde routes.
- 1. basic auth
- 2. 4321

Special observations:
- Domain routes moved from Python source to domain_routes.json so the web UI can manage all previous built-in domain routes.
- web_config.json remains ignored; live sorter processes must be restarted after route edits to pick up changed rules.

tests/test_manage_routes_web.py

@@ -0,0 +1,51 @@
+import base64
+import json
+import tempfile
+import unittest
+from pathlib import Path
+
+from manage_routes_web import basic_auth_ok, load_routes, save_routes, validate_routes
+
+
+class ManageRoutesWebTests(unittest.TestCase):
+    def test_validate_routes_normalizes_domains_and_mailbox(self):
+        routes = validate_routes([
+            {"domains": [" Example.COM ", "example.com"], "mailbox": " Diensten.Test "}
+        ])
+        self.assertEqual(routes, [{"domains": ["example.com"], "mailbox": "Diensten.Test"}])
+
+    def test_validate_routes_rejects_duplicate_domain_across_routes(self):
+        with self.assertRaisesRegex(ValueError, "already used"):
+            validate_routes([
+                {"domains": ["example.com"], "mailbox": "Diensten.Een"},
+                {"domains": ["EXAMPLE.com"], "mailbox": "Diensten.Twee"},
+            ])
+
+    def test_save_routes_writes_backup_and_normalized_json(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            path = Path(tmp) / "domain_routes.json"
+            path.write_text(
+                json.dumps([{"domains": ["old.example"], "mailbox": "Diensten.Oud"}]) + "\n",
+                encoding="utf-8",
+            )
+
+            saved = save_routes(
+                [{"domains": [" New.EXAMPLE "], "mailbox": " Diensten.Nieuw "}],
+                path,
+            )
+
+            self.assertEqual(saved, [{"domains": ["new.example"], "mailbox": "Diensten.Nieuw"}])
+            self.assertEqual(load_routes(path), saved)
+            backup = path.with_suffix(".json.bak")
+            self.assertTrue(backup.exists())
+            self.assertIn("old.example", backup.read_text(encoding="utf-8"))
+
+    def test_basic_auth_ok_accepts_exact_credentials(self):
+        token = base64.b64encode(b"mailcat:secret").decode("ascii")
+        self.assertTrue(basic_auth_ok(f"Basic {token}", "mailcat", "secret"))
+        self.assertFalse(basic_auth_ok(f"Basic {token}", "mailcat", "wrong"))
+        self.assertFalse(basic_auth_ok(None, "mailcat", "secret"))
+
+
+if __name__ == "__main__":
+    unittest.main()