feat: implement API versioning /api/v1/

- All backend routers moved to /api/v1/ prefix
- Frontend BASE_URL updated to /api/v1
- Setup redirect middleware updated to redirect to /api/v1/setup
- Health router path fixed: prefix=/api/v1/health, @router.get('')
- conftest.py: set server_status=online for test fixture
- Created Docs/API_VERSIONING.md with deprecation policy
- Updated Docs/Backend-Development.md with versioning section
- Updated Instructions.md curl examples

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

backend/app/utils/constants.py

@@ -104,3 +104,52 @@ BLOCKLIST_PREVIEW_MAX_LINES: Final[int] = 100
 
 HEALTH_CHECK_INTERVAL_SECONDS: Final[int] = 30
 """How often the background health-check task polls fail2ban."""
+
+# ---------------------------------------------------------------------------
+# Rate limits (per IP)
+# ---------------------------------------------------------------------------
+
+RATE_LIMIT_BANS_BAN_REQUESTS: Final[int] = 100
+"""Max ban requests per IP per minute."""
+
+RATE_LIMIT_BANS_UNBAN_REQUESTS: Final[int] = 100
+"""Max unban requests per IP per minute."""
+
+RATE_LIMIT_BLOCKLIST_IMPORT_REQUESTS: Final[int] = 10
+"""Max blocklist import requests per IP per hour."""
+
+RATE_LIMIT_CONFIG_UPDATE_REQUESTS: Final[int] = 50
+"""Max config update requests per IP per minute."""
+
+RATE_LIMIT_FILTER_UPDATE_REQUESTS: Final[int] = 50
+"""Max filter config update requests per IP per minute."""
+
+RATE_LIMIT_FILTER_CREATE_REQUESTS: Final[int] = 50
+"""Max filter config create requests per IP per minute."""
+
+RATE_LIMIT_FILTER_DELETE_REQUESTS: Final[int] = 50
+"""Max filter config delete requests per IP per minute."""
+
+RATE_LIMIT_ACTION_UPDATE_REQUESTS: Final[int] = 50
+"""Max action config update requests per IP per minute."""
+
+RATE_LIMIT_ACTION_CREATE_REQUESTS: Final[int] = 50
+"""Max action config create requests per IP per minute."""
+
+RATE_LIMIT_ACTION_DELETE_REQUESTS: Final[int] = 50
+"""Max action config delete requests per IP per minute."""
+
+RATE_LIMIT_JAIL_UPDATE_REQUESTS: Final[int] = 100
+"""Max jail config update requests per IP per minute."""
+
+RATE_LIMIT_JAIL_CREATE_REQUESTS: Final[int] = 100
+"""Max jail config create requests per IP per minute."""
+
+RATE_LIMIT_JAIL_DELETE_REQUESTS: Final[int] = 100
+"""Max jail config delete requests per IP per minute."""
+
+RATE_LIMIT_JAIL_ACTIVATE_REQUESTS: Final[int] = 100
+"""Max jail activation requests per IP per minute."""
+
+RATE_LIMIT_JAIL_DEACTIVATE_REQUESTS: Final[int] = 100
+"""Max jail deactivation requests per IP per minute."""