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/repos/combosRepo.js

@@ -0,0 +1,73 @@
+import { v4 as uuidv4 } from "uuid";
+import { getAdapter } from "../driver.js";
+import { parseJson, stringifyJson } from "../helpers/jsonCol.js";
+
+function rowToCombo(row) {
+  if (!row) return null;
+  return {
+    id: row.id,
+    name: row.name,
+    kind: row.kind,
+    models: parseJson(row.models, []),
+    createdAt: row.createdAt,
+    updatedAt: row.updatedAt,
+  };
+}
+
+export async function getCombos() {
+  const db = await getAdapter();
+  const rows = db.all(`SELECT * FROM combos ORDER BY createdAt ASC`);
+  return rows.map(rowToCombo);
+}
+
+export async function getComboById(id) {
+  const db = await getAdapter();
+  const row = db.get(`SELECT * FROM combos WHERE id = ?`, [id]);
+  return rowToCombo(row);
+}
+
+export async function getComboByName(name) {
+  const db = await getAdapter();
+  const row = db.get(`SELECT * FROM combos WHERE name = ?`, [name]);
+  return rowToCombo(row);
+}
+
+export async function createCombo(data) {
+  const db = await getAdapter();
+  const now = new Date().toISOString();
+  const combo = {
+    id: uuidv4(),
+    name: data.name,
+    kind: data.kind || null,
+    models: data.models || [],
+    createdAt: now,
+    updatedAt: now,
+  };
+  db.run(
+    `INSERT INTO combos(id, name, kind, models, createdAt, updatedAt) VALUES(?, ?, ?, ?, ?, ?)`,
+    [combo.id, combo.name, combo.kind, stringifyJson(combo.models), combo.createdAt, combo.updatedAt]
+  );
+  return combo;
+}
+
+export async function updateCombo(id, data) {
+  const db = await getAdapter();
+  let result = null;
+  db.transaction(() => {
+    const row = db.get(`SELECT * FROM combos WHERE id = ?`, [id]);
+    if (!row) return;
+    const merged = { ...rowToCombo(row), ...data, updatedAt: new Date().toISOString() };
+    db.run(
+      `UPDATE combos SET name = ?, kind = ?, models = ?, updatedAt = ? WHERE id = ?`,
+      [merged.name, merged.kind, stringifyJson(merged.models || []), merged.updatedAt, id]
+    );
+    result = merged;
+  });
+  return result;
+}
+
+export async function deleteCombo(id) {
+  const db = await getAdapter();
+  const res = db.run(`DELETE FROM combos WHERE id = ?`, [id]);
+  return (res?.changes ?? 0) > 0;
+}