refactor: split module.nix into per-service modules

Replace the 1301-line monolithic module.nix with focused modules:
- modules/servarr.nix  (Sonarr/Radarr/Prowlarr)
- modules/bazarr.nix   (Bazarr provider connections)
- modules/jellyseerr.nix (Jellyseerr quality profiles)
- modules/default.nix  (import aggregator)

Python scripts (from prior commit) are referenced as standalone
files via PYTHONPATH, with config passed as a JSON file argument.

New options and behavioral changes:
- Add bindAddress option to all services (default 127.0.0.1)
- Change healthChecks default from false to true
- Replace hardcoded wg.service dependency with configurable
  networkNamespaceService option
- Add systemd hardening: PrivateTmp, NoNewPrivileges, ProtectHome,
  ProtectKernelTunables/Modules, ProtectControlGroups,
  RestrictSUIDSGID, SystemCallArchitectures=native

Test updates:
- Extract mock qBittorrent/SABnzbd servers into tests/lib/mocks.nix
- Add healthChecks=false to tests not exercising health checks
- Fix duplicate wait_for_unit calls in integration test

modules/default.nix

@@ -0,0 +1,8 @@
+{ ... }:
+{
+  imports = [
+    ./servarr.nix
+    ./bazarr.nix
+    ./jellyseerr.nix
+  ];
+}