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/docker-build.sh

@@ -8,9 +8,9 @@
 # the AppImage links against, and building on the host instead means shipping
 # whatever that host happens to run.
 #
-# Honours VOCALINUX_APPIMAGE_REQUIRE_VULKAN / _SKIP_VULKAN like build.sh, and
-# keeps glslc and the pywhispercpp Vulkan build in VOCALINUX_APPIMAGE_CACHE
-# (~/.cache/vocalinux-appimage by default) so the next build reuses them.
+# Honours VOCULINUX_APPIMAGE_REQUIRE_VULKAN / _SKIP_VULKAN like build.sh, and
+# keeps glslc and the pywhispercpp Vulkan build in VOCULINUX_APPIMAGE_CACHE
+# (~/.cache/voculinux-appimage by default) so the next build reuses them.
 set -euo pipefail
 
 REPO_ROOT="$(cd "$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")/../.." && pwd)"
@@ -20,7 +20,7 @@ if [ -z "$IMAGE" ]; then
     exit 1
 fi
 
-CACHE="${VOCALINUX_APPIMAGE_CACHE:-${XDG_CACHE_HOME:-$HOME/.cache}/vocalinux-appimage}"
+CACHE="${VOCULINUX_APPIMAGE_CACHE:-${XDG_CACHE_HOME:-$HOME/.cache}/voculinux-appimage}"
 mkdir -p "$CACHE"
 
 # The wheel and output dir are given as host paths; the repo is mounted at the
@@ -31,9 +31,9 @@ exec docker run --rm \
     --security-opt seccomp=unconfined \
     -v "$REPO_ROOT:$REPO_ROOT" -w "$REPO_ROOT" \
     -v "$CACHE:/cache" \
-    -e VOCALINUX_APPIMAGE_CACHE=/cache \
-    -e VOCALINUX_APPIMAGE_REQUIRE_VULKAN \
-    -e VOCALINUX_APPIMAGE_SKIP_VULKAN \
+    -e VOCULINUX_APPIMAGE_CACHE=/cache \
+    -e VOCULINUX_APPIMAGE_REQUIRE_VULKAN \
+    -e VOCULINUX_APPIMAGE_SKIP_VULKAN \
     -e CMAKE_BUILD_PARALLEL_LEVEL \
     -e HOST_UID="$(id -u)" \
     -e HOST_GID="$(id -g)" \