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

scripts/test_remote_server.py

@@ -1,8 +1,8 @@
 #!/usr/bin/env python3
 """
-Vocalinux Remote API Test Server
+Voculinux Remote API Test Server
 
-A simple mock server for testing Vocalinux's remote API feature.
+A simple mock server for testing Voculinux's remote API feature.
 Supports whisper.cpp (/inference) and OpenAI/FunASR-compatible
 (/v1/audio/transcriptions) formats.
 
@@ -22,7 +22,7 @@ from http.server import BaseHTTPRequestHandler, HTTPServer
 
 
 class RemoteAPITestHandler(BaseHTTPRequestHandler):
-    """HTTP request handler for testing Vocalinux remote API."""
+    """HTTP request handler for testing Voculinux remote API."""
 
     def log_message(self, format, *args):
         """Custom log format with timestamp."""
@@ -37,7 +37,7 @@ class RemoteAPITestHandler(BaseHTTPRequestHandler):
             self.end_headers()
             response = {
                 "status": "ok",
-                "message": "Vocalinux Remote API Test Server",
+                "message": "Voculinux Remote API Test Server",
                 "endpoints": [
                     "/inference (whisper.cpp format)",
                     "/v1/audio/transcriptions (OpenAI/FunASR format)",
@@ -138,7 +138,7 @@ class RemoteAPITestHandler(BaseHTTPRequestHandler):
         if "test" in filename.lower():
             return "This is a test transcription from the mock server."
         elif "hello" in filename.lower():
-            return "Hello, this is Vocalinux testing the remote API."
+            return "Hello, this is Voculinux testing the remote API."
         elif "long" in filename.lower():
             return (
                 "This is a longer transcription to test how the system handles "
@@ -159,7 +159,7 @@ class DelayedHTTPServer(HTTPServer):
 
 def main():
     parser = argparse.ArgumentParser(
-        description="Vocalinux Remote API Test Server"
+        description="Voculinux Remote API Test Server"
     )
     parser.add_argument(
         "--port",
@@ -183,7 +183,7 @@ def main():
     args = parser.parse_args()
 
     print("=" * 60)
-    print("Vocalinux Remote API Test Server")
+    print("Voculinux Remote API Test Server")
     print("=" * 60)
     print(f"Listening on: http://{args.host}:{args.port}")
     print(f"Processing delay: {args.delay}s")