feat: working .deb build for edgeguard-api + meta

scripts/apt-repo/build-package.sh produces:
  - edgeguard-api_<ver>_<arch>.deb  (3 Go binaries, systemd units,
    /etc/edgeguard/edgeguard.yaml as conffile)
  - edgeguard-ui_<ver>_all.deb       (skipped while management-ui/dist
    is empty)
  - edgeguard_<ver>_all.deb          (meta, Depends api+ui)

Verified locally on amd64:
  - go build ./...           ✓
  - make deb-amd64           ✓
  - api binary serves        ✓
    GET /api/health → 200 {"status":"ok","version":"0.0.1-dev"}
  - dpkg-deb -I + -c clean   ✓

packaging/debian/edgeguard-ui/DEBIAN/control

@@ -6,7 +6,7 @@ Homepage: https://edgeguard.netcell-it.de
 Description: EdgeGuard — management UI (static React build)
  React 19 + Ant Design 6 single-page admin UI for EdgeGuard.
  Served by the Angie reverse proxy bundled in edgeguard-api.
-Depends: edgeguard-api (= ${binary:Version}), angie
+Depends: edgeguard-api (= __VERSION__), angie
 Section: admin
 Priority: optional
 Installed-Size: 0