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/aliasRepo.js

@@ -0,0 +1,62 @@
+import { getAdapter } from "../driver.js";
+import { parseJson, stringifyJson } from "../helpers/jsonCol.js";
+import { makeKv } from "../helpers/kvStore.js";
+
+const aliasKv = makeKv("modelAliases");
+const customKv = makeKv("customModels");
+const mitmKv = makeKv("mitmAlias");
+
+// modelAliases: key=alias, value=modelString
+export async function getModelAliases() {
+  return await aliasKv.getAll();
+}
+
+export async function setModelAlias(alias, model) {
+  await aliasKv.set(alias, model);
+}
+
+export async function deleteModelAlias(alias) {
+  await aliasKv.remove(alias);
+}
+
+// customModels: key=`${providerAlias}|${id}|${type}`, value=full model object
+function customKey(providerAlias, id, type) {
+  return `${providerAlias}|${id}|${type}`;
+}
+
+export async function getCustomModels() {
+  const all = await customKv.getAll();
+  return Object.values(all);
+}
+
+// Atomic check-then-insert inside transaction to prevent duplicate races
+export async function addCustomModel({ providerAlias, id, type = "llm", name }) {
+  const k = customKey(providerAlias, id, type);
+  const db = await getAdapter();
+  let added = false;
+  db.transaction(() => {
+    const row = db.get(`SELECT 1 FROM kv WHERE scope = 'customModels' AND key = ?`, [k]);
+    if (row) return;
+    const value = stringifyJson({ providerAlias, id, type, name: name || id });
+    db.run(`INSERT INTO kv(scope, key, value) VALUES('customModels', ?, ?)`, [k, value]);
+    added = true;
+  });
+  return added;
+}
+
+export async function deleteCustomModel({ providerAlias, id, type = "llm" }) {
+  await customKv.remove(customKey(providerAlias, id, type));
+}
+
+// mitmAlias: key=toolName, value=mappings object
+export async function getMitmAlias(toolName) {
+  if (toolName) {
+    const v = await mitmKv.get(toolName);
+    return v || {};
+  }
+  return await mitmKv.getAll();
+}
+
+export async function setMitmAliasAll(toolName, mappings) {
+  await mitmKv.set(toolName, mappings || {});
+}