Fix SQLite LIKE wildcard escaping in IP filter queries

- Add escape_like() helper to escape % and _ wildcards in LIKE queries
- Update fail2ban_db_repo.get_history_page() to use escaping
- Update history_archive_repo.get_archived_history() to use escaping
- Add ESCAPE clause to all LIKE queries
- Add comprehensive unit tests for escape_like function
- Add integration tests for LIKE wildcard handling
- Document LIKE escaping best practices in Backend-Development.md

Fixes TASK-017: Prevent unintended LIKE matches when IP filter contains
special characters like underscore or percent sign.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/tests/test_utils/test_fail2ban_db_utils.py

@@ -0,0 +1,60 @@
+"""Tests for fail2ban_db_utils module."""
+
+from app.utils.fail2ban_db_utils import escape_like
+
+
+def test_escape_like_percent_sign() -> None:
+    """Test escaping of percent signs (% wildcard)."""
+    assert escape_like("10.0.0%") == "10.0.0\\%"
+
+
+def test_escape_like_underscore() -> None:
+    """Test escaping of underscores (_ wildcard)."""
+    assert escape_like("10.0.0_1") == "10.0.0\\_1"
+
+
+def test_escape_like_backslash() -> None:
+    """Test escaping of backslashes."""
+    assert escape_like("10.0.0\\") == "10.0.0\\\\"
+
+
+def test_escape_like_combined_wildcards() -> None:
+    """Test escaping when both % and _ are present."""
+    assert escape_like("10.0_%") == "10.0\\_\\%"
+
+
+def test_escape_like_combined_with_backslash() -> None:
+    """Test escaping backslash first, then wildcards."""
+    assert escape_like("10\\0_%") == "10\\\\0\\_\\%"
+
+
+def test_escape_like_normal_ip() -> None:
+    """Test that normal IPs pass through unchanged (dots are not wildcards)."""
+    assert escape_like("10.0.0.1") == "10.0.0.1"
+
+
+def test_escape_like_empty_string() -> None:
+    """Test escaping empty string."""
+    assert escape_like("") == ""
+
+
+def test_escape_like_only_backslash() -> None:
+    """Test string with only backslashes."""
+    assert escape_like("\\\\") == "\\\\\\\\"
+
+
+def test_escape_like_only_percent() -> None:
+    """Test string with only percent signs."""
+    assert escape_like("%%%") == "\\%\\%\\%"
+
+
+def test_escape_like_only_underscore() -> None:
+    """Test string with only underscores."""
+    assert escape_like("___") == "\\_\\_\\_"
+
+
+def test_escape_like_backslash_before_wildcard() -> None:
+    """Test that backslash before wildcard is properly escaped."""
+    result = escape_like("10\\_%")
+    # Expected: backslash → \\ , underscore → \_ , percent → \%
+    assert result == "10\\\\\\_\\%"