feat: add settings normalization and status storage

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/lib/storage.js

@@ -0,0 +1,34 @@
+export const DEFAULT_SETTINGS = { apiKey: '', threshold: 5, minViews: 10000 };
+
+const toNumber = (value) => (value === null || value === undefined || value === '' ? NaN : Number(value));
+
+export function normalizeSettings(raw = {}) {
+  const threshold = toNumber(raw.threshold);
+  const minViews = toNumber(raw.minViews);
+  return {
+    apiKey: typeof raw.apiKey === 'string' ? raw.apiKey.trim() : DEFAULT_SETTINGS.apiKey,
+    threshold: Number.isFinite(threshold) && threshold > 0 ? threshold : DEFAULT_SETTINGS.threshold,
+    minViews: Number.isFinite(minViews) && minViews >= 0 ? Math.floor(minViews) : DEFAULT_SETTINGS.minViews,
+  };
+}
+
+export async function getSettings() {
+  const { settings } = await chrome.storage.local.get('settings');
+  return normalizeSettings(settings);
+}
+
+export async function saveSettings(raw) {
+  const settings = normalizeSettings(raw);
+  await chrome.storage.local.set({ settings });
+  return settings;
+}
+
+// Status is { state: 'ok' | 'no-key' | 'invalid-key' | 'quota', message?, until? }.
+export async function getStatus() {
+  const { status } = await chrome.storage.local.get('status');
+  return status ?? { state: 'ok' };
+}
+
+export async function setStatus(status) {
+  await chrome.storage.local.set({ status });
+}