feat(db): migrate from lowdb to SQLite with repos pattern

- Add modular DB layer (adapters, migrations, repos, helpers)
- Replace localDb/usageDb/requestDetailsDb monoliths with repos
- Add Tailscale tunnel integration & status check API
- Add /api/cli-tools/all-statuses aggregated endpoint
- Add settingsStore (Zustand) and mitm/dbReader
- Add DB unit tests (benchmark, concurrent, migration, vs-lowdb)

src/lib/db/migrations/index.js

@@ -0,0 +1,10 @@
+// Migration registry — append new entries when schema changes.
+// Each migration: { version: number, name: string, up(db): void }
+// Versions MUST be unique and monotonically increasing.
+import m001 from "./001-initial.js";
+
+export const MIGRATIONS = [m001].sort((a, b) => a.version - b.version);
+
+export function latestVersion() {
+  return MIGRATIONS.length ? MIGRATIONS[MIGRATIONS.length - 1].version : 0;
+}