chore(deps): drop better-sqlite3 and its desktop packaging support

The SQLite write into OpenCode's database was the only consumer of
better-sqlite3 in the repository. Everything that existed to ship its native
binary went with it:

- the dependency in @openchamber/web and @openchamber/electron
- the afterPack hook staging better_sqlite3.node into app.asar.unpacked
- a dedicated @electron/rebuild pass (onlyModules) and its binary assertion,
  so desktop packaging now runs one native rebuild instead of two
- the bundler external entry and the AppImage required-native-module check

Desktop packaging, the AppImage verification tests, and the extension bundle
were re-validated after a clean reinstall, so no stale module could satisfy a
missed import.

packages/electron/scripts/verify-linux-appimage.mjs

@@ -13,7 +13,7 @@ const ELF_MACHINE = { x64: 62, arm64: 183 };
 // sherpa-onnx-node loads this Node-API addon from its platform-specific prebuilt
 // package in the separate server worker, so verify its architecture here rather
 // than Electron-rebuilding it with the source-built modules.
-const REQUIRED_NATIVE_MODULES = ['better_sqlite3.node', 'pty.node', 'sherpa-onnx.node'];
+const REQUIRED_NATIVE_MODULES = ['pty.node', 'sherpa-onnx.node'];
 
 /** electron-builder AppImage arch token: x64 → x86_64, arm64 → arm64 */
 export const linuxAppImageArchSuffix = (architecture) => (