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

tests/test_logging_manager.py

@@ -129,7 +129,7 @@ class TestLoggingManager:
 
         manager = lm.LoggingManager(max_records=10)
         try:
-            assert manager.logs_dir == tmp_path / "vocalinux" / "logs"
+            assert manager.logs_dir == tmp_path / "voculinux" / "logs"
             assert manager.logs_dir.is_dir()
         finally:
             root_logger.removeHandler(manager.handler)
@@ -296,7 +296,7 @@ class TestLoggingManager:
         record2 = LogRecord(
             timestamp=datetime.now(),
             level="INFO",
-            logger_name="vocalinux.speech.test",
+            logger_name="voculinux.speech.test",
             message="Speech message",
         )
         logging_manager.add_log_record(record1)
@@ -353,7 +353,7 @@ class TestLoggingManager:
             with open(filepath, "r") as f:
                 content = f.read()
 
-            assert "VocaLinux Log Export" in content
+            assert "Voculinux Log Export" in content
             assert "Export test message" in content
         finally:
             if os.path.exists(filepath):
@@ -451,7 +451,7 @@ class TestLoggingManager:
         record2 = LogRecord(
             timestamp=timestamp2,
             level="ERROR",
-            logger_name="vocalinux.speech.test",
+            logger_name="voculinux.speech.test",
             message="Message 2",
         )
         logging_manager.add_log_record(record1)
@@ -462,7 +462,7 @@ class TestLoggingManager:
         assert stats["total"] == 2
         assert stats["by_level"]["INFO"] == 1
         assert stats["by_level"]["ERROR"] == 1
-        assert "vocalinux" in stats["by_module"]
+        assert "voculinux" in stats["by_module"]
         assert stats["oldest"] == timestamp1
         assert stats["newest"] == timestamp2