Fix Spotify plugin loading in daemon mode

[dialupdisaster]

Summary

• register actions with IDs derived from the canonical manifest plugin ID
• retain legacy action registrations for compatibility
• migrate existing page and backup action IDs during plugin installation

Why

StreamController daemon mode uses the action ID namespace to select the plugin folder to preload. The existing dev_ReneLu_SpotifyControl namespace does not match the installed com_ReneLu_spotifyControl folder, so the plugin is skipped until the GUI loads all plugins.

Fixes #70

Testing

• python3 -m compileall -q .
• git diff --check
• exercised migration against temporary key, dial, backup, malformed, and unrelated action data
• deployed locally and confirmed existing page IDs migrated
• confirmed normal StreamController startup loads the plugin and starts its backend without missing Spotify action warnings

The installed Flatpak build rejected --daemon-only, so the exact daemon command could not be exercised locally.