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

SECURITY.md

@@ -20,7 +20,7 @@ Do not open a public GitHub issue for security vulnerabilities.
 
 **Preferred:** email the maintainer at **jatinkrmalik@gmail.com** with subject:
 
-`Vocalinux Security Vulnerability Report`
+`Voculinux Security Vulnerability Report`
 
 Include:
 
@@ -35,7 +35,7 @@ If email is unavailable, use [GitHub private vulnerability reporting](https://gi
 
 ## Privacy design
 
-Vocalinux is built for local-first dictation:
+Voculinux is built for local-first dictation:
 
 - Local engines process audio on-device after you download a model
 - No Voca account is required for local engines
@@ -62,8 +62,8 @@ When the user enables **Remote API**, audio is uploaded to the configured server
 
 | Path | Purpose | Permissions (typical) |
 |------|---------|------------------------|
-| `~/.config/vocalinux/` | Configuration | User-only (mode 700) |
-| `~/.local/share/vocalinux/` | Data and models | User-only (mode 700) |
+| `~/.config/voculinux/` | Configuration | User-only (mode 700) |
+| `~/.local/share/voculinux/` | Data and models | User-only (mode 700) |
 
 ### Known limitations