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/web/package.json

@@ -28,7 +28,6 @@
     "@opencode-ai/sdk": "1.18.11",
     "@simplewebauthn/server": "13.3.1",
     "adm-zip": "^0.5.16",
-    "better-sqlite3": "^12.10.0",
     "bun-pty": "^0.4.5",
     "compression": "^1.8.1",
     "cron-parser": "^4.9.0",