Add multi-user auth, admin panel, and timezone support; rename to Yolkbook

- Rename app from Eggtracker to Yolkbook throughout
- Add JWT-based authentication (python-jose, passlib/bcrypt)
- Add users table; all data tables gain user_id FK for full data isolation
- Super admin credentials sourced from ADMIN_USERNAME/ADMIN_PASSWORD env vars,
  synced on every startup; orphaned rows auto-assigned to admin post-migration
- Login page with self-registration; JWT stored in localStorage (30-day expiry)
- Admin panel (/admin): list users, reset passwords, disable/enable, delete,
  and impersonate (Login As) with Return to Admin banner
- Settings modal (gear icon in nav): timezone selector and change password
- Timezone stored per-user; stats date windows computed in user's timezone;
  date input setToday() respects user timezone via Intl API
- migrate_v2.sql for existing single-user installs
- Auto-migration adds timezone column to users on startup
- Updated README with full setup, auth, admin, and migration docs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nginx/html/js/api.js

@@ -2,10 +2,21 @@
 
 const API = {
     async _fetch(url, options = {}) {
+        const token = localStorage.getItem('token');
+        const headers = { 'Content-Type': 'application/json' };
+        if (token) headers['Authorization'] = `Bearer ${token}`;
+
         const res = await fetch(url, {
-            headers: { 'Content-Type': 'application/json' },
+            headers,
             ...options,
         });
+
+        if (res.status === 401) {
+            localStorage.removeItem('token');
+            window.location.href = '/login';
+            return;
+        }
+
         if (!res.ok) {
             const err = await res.json().catch(() => ({ detail: res.statusText }));
             throw new Error(err.detail || `Request failed (${res.status})`);
@@ -27,13 +38,13 @@ function showMessage(el, text, type = 'success') {
     setTimeout(() => { el.className = 'message'; }, 4000);
 }
 
-// Set an input[type=date] to today's date (using local time, not UTC)
+// Set an input[type=date] to today's date in the user's configured timezone
 function setToday(inputEl) {
-    const now = new Date();
-    const y = now.getFullYear();
-    const m = String(now.getMonth() + 1).padStart(2, '0');
-    const d = String(now.getDate()).padStart(2, '0');
-    inputEl.value = `${y}-${m}-${d}`;
+    const tz = (typeof Auth !== 'undefined' && Auth.getUser()?.timezone)
+        || Intl.DateTimeFormat().resolvedOptions().timeZone
+        || 'UTC';
+    // en-CA locale produces YYYY-MM-DD which is what date inputs expect
+    inputEl.value = new Date().toLocaleDateString('en-CA', { timeZone: tz });
 }
 
 // Format YYYY-MM-DD → MM/DD/YYYY for display