refactor(backend): clean up models setup, improve ip utils, add adr docs

- Extract ADR documents for architectural decisions (SQLite, FastAPI, React, APScheduler, Scheduler)
- Refactor setup.py: improve code structure and readability
- Add IP validation utilities with test coverage
- Update frontend components (BanTable, HistoryPage)
- Add pre-commit hooks and CONTRIBUTING.md
- Add .editorconfig for consistent coding standards

backend/tests/test_services/test_ip_utils.py

@@ -77,6 +77,9 @@ class TestNormaliseIp:
     def test_normalise_ip_ipv6_compressed(self) -> None:
         assert normalise_ip("2001:0db8:0000:0000:0000:0000:0000:0001") == "2001:db8::1"
 
+    def test_normalise_ip_ipv4_mapped_ipv6_to_ipv4(self) -> None:
+        assert normalise_ip("::ffff:192.168.1.1") == "192.168.1.1"
+
     def test_normalise_ip_invalid_raises_value_error(self) -> None:
         with pytest.raises(ValueError):
             normalise_ip("not-an-ip")