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

resources/icons/scalable/voculinux-microphone-off.svg

@@ -1,4 +1,4 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 1024 1024" role="img" aria-label="Vocalinux idle">
+<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 1024 1024" role="img" aria-label="Voculinux idle">
   <!-- Opaque disc for StatusNotifier trays (~22px) -->
   <circle cx="512" cy="512" r="480" fill="#0B1A15"/>
   <g transform="translate(28.386 32.619) scale(2.116474)">

resources/icons/scalable/voculinux-microphone-process.svg

@@ -1,4 +1,4 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 1024 1024" role="img" aria-label="Vocalinux processing">
+<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 1024 1024" role="img" aria-label="Voculinux processing">
   <!-- Opaque disc for StatusNotifier trays (~22px) -->
   <circle cx="512" cy="512" r="480" fill="#A86108"/>
   <g transform="translate(28.386 32.619) scale(2.116474)">

resources/icons/scalable/voculinux-microphone.svg

@@ -1,4 +1,4 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 1024 1024" role="img" aria-label="Vocalinux recording">
+<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 1024 1024" role="img" aria-label="Voculinux recording">
   <!-- Opaque disc for StatusNotifier trays (~22px) -->
   <circle cx="512" cy="512" r="480" fill="#C73D38"/>
   <g transform="translate(28.386 32.619) scale(2.116474)">

resources/icons/scalable/voculinux.svg

@@ -1,4 +1,4 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 460 460" width="460" height="460" role="img" aria-label="Vocalinux">
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 460 460" width="460" height="460" role="img" aria-label="Voculinux">
   <circle cx="229" cy="231.5" r="221.5" fill="#0F6B57"/>
   <path d="M 164 127 A 65 65 0 0 1 294 127 L 294 224 A 65 65 0 0 1 164 224 Z" fill="#F2F6F2"/>
   <path d="M 144.87 202.02 A 87 87 0 1 0 312.13 202.02" fill="none" stroke="#F2F6F2" stroke-width="18" stroke-linecap="round"/>