pkg: build a local .deb; de-duplicate onto DAEMON's systemd/nativehost/man page

DAEMON landed packaging/nativehost/, packaging/systemd/{velox.service,velox.socket}
(real sd_listen_fds() socket activation) and cli/man/velox.1 on main while this was
in flight, duplicating paths this branch had drafted independently. Per CLAUDE.md
(packaging/nativehost/ is DAEMON's; the rest of packaging/ is PKG/QA's), DAEMON's
copies are kept as the single source and this branch's packaging/native-messaging/,
packaging/man/velox.1 and stale packaging/systemd/velox.service are dropped rather
than maintained twice. The root CMakeLists.txt's install() rules now point at
DAEMON's paths directly, install both systemd units (not just velox.service), and
docs/07-packaging.md / packaging/README.md no longer claim there's no socket
activation — there is, and this package now ships it.

Adds the local-test-only .deb itself: debian/{control,rules,postinst,postrm,
changelog,copyright}, a placeholder icon set, the desktop entry and PKG/QA's own
man pages (veloxd.8, velox-gui.1 — velox.1 stays DAEMON's). libveloxcore stays
static (no consumer needs a .so yet); pairing has no real approval UI in this
build (D1 unbuilt), so postinst and packaging/README.md both say VELOX_PAIR_AUTO=1
is required and print it prominently. No PPA, no GPG — local dpkg -i only.

Verified live: dpkg-buildpackage -us -uc -b, dpkg -i, socket activation (systemctl
--user enable --now velox.socket), `velox ls` against the running daemon, lintian
clean, dpkg -r removes the manifest/units and leaves $XDG_DATA_HOME/velox alone.

.gitignore now excludes dpkg-buildpackage's debhelper build tree and obj-*/ (the
debuild output dir) — debian/control et al. stay tracked, everything debhelper
regenerates does not.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_0176u3fTrxegrGNm2yC7r69W

debian/control

@@ -0,0 +1,35 @@
+Source: velox
+Section: net
+Priority: optional
+Maintainer: Velox Local Test Build <[email protected]>
+Build-Depends: debhelper-compat (= 13),
+               cmake (>= 3.28),
+               ninja-build,
+               pkg-config,
+               g++ (>= 13),
+               qt6-base-dev,
+               qt6-tools-dev,
+               qt6-tools-dev-tools,
+               qt6-svg-dev,
+               libcurl4-openssl-dev,
+               libssl-dev,
+               libsqlite3-dev,
+               nlohmann-json3-dev,
+               libsecret-1-dev
+Standards-Version: 4.6.2
+Rules-Requires-Root: no
+
+Package: velox
+Architecture: amd64
+Depends: ${shlibs:Depends}, ${misc:Depends}
+Description: IDM-class download manager for Linux (local test build)
+ Velox is a segmented, resumable download manager for Linux: a daemon
+ (veloxd) that does the transfer work, a Qt GUI, a CLI, and a Firefox
+ extension for capture.
+ .
+ This package ships veloxd, the velox CLI, the velox-gui Qt client and
+ velox-nmhost, the Firefox native-messaging host.
+ .
+ THIS IS A LOCAL TEST BUILD, not a release: it uses a placeholder app
+ icon and has no real pairing-approval UI (see /usr/share/doc/velox, or
+ packaging/README.md in the source tree, for both limitations).