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

packaging/appimage/native-cache-id.sh

@@ -5,16 +5,16 @@
 # from it), every pin in tool_checksums.txt, the cmake/ninja pins in
 # requirements/appimage-tools.txt, the Vulkan flags in build.sh, and the
 # pywhispercpp sdist install.sh names. It does not depend on the rest of the
-# Vocalinux sources, so this id ignores the git commit and the Actions run id
+# Voculinux sources, so this id ignores the git commit and the Actions run id
 # on purpose: putting either in the cache key would rebuild on every push.
 set -euo pipefail
 
 here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 repo="$(cd "$here/../.." && pwd)"
-pins="${VOCALINUX_PINS:-$repo/packaging/appimage/tool_checksums.txt}"
-install_sh="${VOCALINUX_INSTALL_SH:-$repo/install.sh}"
-tools="${VOCALINUX_APPIMAGE_TOOLS:-$repo/requirements/appimage-tools.txt}"
-build_sh="${VOCALINUX_BUILD_SH:-$repo/packaging/appimage/build.sh}"
+pins="${VOCULINUX_PINS:-$repo/packaging/appimage/tool_checksums.txt}"
+install_sh="${VOCULINUX_INSTALL_SH:-$repo/install.sh}"
+tools="${VOCULINUX_APPIMAGE_TOOLS:-$repo/requirements/appimage-tools.txt}"
+build_sh="${VOCULINUX_BUILD_SH:-$repo/packaging/appimage/build.sh}"
 
 base="$(awk '$1=="base-image" {print $3; exit}' "$pins")"
 if [ -z "$base" ]; then