refactor(js): app.js 를 브라우저 네이티브 ESM 모듈로 분할

public/js/{util,ui,reactions,modals,comments,feed,main}.js 로 분리하고
dashboard/project 에서 <script type="module" src="/public/js/main.js"> 로 로드.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

public/js/ui.js

@@ -0,0 +1,59 @@
+// 헤더 UI — 테마 토글 · 사용자 메뉴 · 로고 이스터에그.
+import { $, toast, burstThumbs } from "./util.js";
+
+function applyTheme(t) { document.documentElement.setAttribute("data-aidev-theme", t); }
+
+export function initTheme() {
+  const btn = $("#themeToggle");
+  if (!btn) return;
+  btn.addEventListener("click", () => {
+    const cur = document.documentElement.getAttribute("data-aidev-theme") === "dark" ? "dark" : "light";
+    const next = cur === "dark" ? "light" : "dark";
+    applyTheme(next);
+    try { localStorage.setItem("aidev-theme", next); } catch (e) {}
+  });
+}
+
+export function initUserMenu() {
+  const btn = $("#userMenuBtn"), pop = $("#userMenuPop");
+  if (!btn || !pop) return;
+  btn.addEventListener("click", (e) => {
+    e.stopPropagation();
+    const open = pop.hidden;
+    pop.hidden = !open;
+    btn.setAttribute("aria-expanded", open ? "true" : "false");
+  });
+  document.addEventListener("click", (e) => {
+    if (!pop.hidden && !pop.contains(e.target) && !btn.contains(e.target)) {
+      pop.hidden = true; btn.setAttribute("aria-expanded", "false");
+    }
+  });
+}
+
+// 로고를 4번 빠르게 클릭하면 흔들림 + 👍 (단일 클릭은 잠시 뒤 홈 이동)
+export function initLogoEgg() {
+  const logo = $("#brandLink");
+  if (!logo) return;
+  let clicks = 0, timer = null, navTimer = null;
+  const mark = $(".brand-mark", logo);
+  logo.addEventListener("click", (e) => {
+    e.preventDefault();
+    clicks++;
+    clearTimeout(timer);
+    timer = setTimeout(() => { clicks = 0; }, 700);
+    if (navTimer) clearTimeout(navTimer);
+    if (clicks >= 4) {
+      clicks = 0;
+      if (mark) {
+        mark.style.animation = "aidev-shake .5s ease";
+        const old = mark.style.filter;
+        mark.style.filter = "hue-rotate(180deg) saturate(1.5)";
+        setTimeout(() => { mark.style.animation = ""; mark.style.filter = old; }, 520);
+      }
+      burstThumbs();
+      toast('🌈 git commit -m "found an easter egg"');
+      return;
+    }
+    navTimer = setTimeout(() => { window.location.href = logo.getAttribute("href") || "/"; }, 320);
+  });
+}