feat(identity): rename user-visible identity to voculinux with one-time legacy import

The fork takes its own name everywhere a user can see it: binaries
(voculinux, voculinux-gui), desktop entry, autostart, tray, D-Bus
namespace (com.voculinux.Voculinux, no alias for the old name),
config/data/cache dirs, single-instance lock, IBus engine identity,
tray icons, resource prefixes, VOCULINUX_* environment names, and the
update-checker user agent. The internal Python module stays vocalinux
and the distribution metadata keeps the upstream URLs as provenance.

On first run a previous Vocalinux install's config.json, custom
dictionary, and portal restore token are copied once into the new
locations (new config always wins, no merge, no write-back); models
re-resolve through the pinned-checksum download path. An offline
naming-sweep test proves no old-name strings remain on user-visible
surfaces outside the allowlist.

Refs #18

SUPPORT.md

@@ -1,6 +1,6 @@
 # Support
 
-Where to get help with Vocalinux.
+Where to get help with Voculinux.
 
 ## Documentation
 
@@ -14,7 +14,7 @@ Where to get help with Vocalinux.
 | Distros and sessions | [docs/DISTRO_COMPATIBILITY.md](docs/DISTRO_COMPATIBILITY.md) |
 | Remote transcription API | [docs/HTTP_REMOTE.md](docs/HTTP_REMOTE.md) |
 | Full index | [docs/README.md](docs/README.md) |
-| Website | [vocalinux.com](https://vocalinux.com) |
+| Website | [voculinux.com](https://voculinux.com) |
 
 ## Community
 
@@ -25,7 +25,7 @@ Where to get help with Vocalinux.
 | [Bug report](https://github.com/VocaHQ/vocalinux/issues/new?template=bug_report.md) | Something is broken |
 | [Feature request](https://github.com/VocaHQ/vocalinux/issues/new?template=feature_request.md) | New capability proposals |
 
-When filing a bug, include OS/distro, `vocalinux --version`, install method, display server (X11/Wayland), engine, and a `vocalinux --debug` snippet.
+When filing a bug, include OS/distro, `voculinux --version`, install method, display server (X11/Wayland), engine, and a `voculinux --debug` snippet.
 
 ## Security