Initial commit: habit tracker PWA with Google OAuth, push notifications

FastAPI + SQLAlchemy/Alembic + MariaDB backend with Jinja2/htmx/Alpine
server-rendered frontend. Multi-user via Google OAuth, daily habit
tracking, monthly/weekly history views, Web Push reminders via
APScheduler, and PWA support (manifest, service worker, offline caching).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/static/js/app.js

@@ -0,0 +1,35 @@
+(function () {
+  if ("serviceWorker" in navigator) {
+    window.addEventListener("load", function () {
+      navigator.serviceWorker.register("/service-worker.js").catch(function (err) {
+        console.error("서비스워커 등록 실패", err);
+      });
+    });
+  }
+
+  function isIos() {
+    return /iphone|ipad|ipod/i.test(window.navigator.userAgent);
+  }
+
+  function isStandalone() {
+    return (
+      ("standalone" in window.navigator && window.navigator.standalone) ||
+      window.matchMedia("(display-mode: standalone)").matches
+    );
+  }
+
+  document.addEventListener("DOMContentLoaded", function () {
+    var banner = document.getElementById("ios-install-banner");
+    if (!banner) return;
+    var dismissed = localStorage.getItem("iosInstallBannerDismissed");
+    if (isIos() && !isStandalone() && !dismissed) {
+      banner.style.display = "flex";
+    }
+  });
+
+  window.dismissIosInstallBanner = function () {
+    var banner = document.getElementById("ios-install-banner");
+    if (banner) banner.style.display = "none";
+    localStorage.setItem("iosInstallBannerDismissed", "1");
+  };
+})();