make app name and purpose machine-readable on the landing page

Google OAuth branding review rejected the app twice with "no description of
the app purpose on the homepage" and "app name does not match the homepage",
even though both were present in Korean. Two likely causes, both addressed:

- The h1 wrapped an alt="" logo image before the text, so the app name could
  not be extracted from it. The image now sits outside the h1, leaving the
  heading as plain text.
- The page was Korean-only. The app name is now "해빗랩 (HabitLab)" (matching
  the console exactly), and the title, meta description and a new About
  section carry an English description of the app purpose and its use of
  Google account data.

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

app/static/css/style.css

@@ -1136,18 +1136,25 @@ label {
   text-align: center;
 }
 
-/* 앱 이름을 담은 h1 — 시각적으로는 작은 브랜드 라벨이지만 문서 구조상 최상위 제목이다. */
+/* 로고 + 앱 이름 h1 묶음. h1은 시각적으로 작은 브랜드 라벨이지만 문서 구조상 최상위 제목이다. */
 .landing-brand {
   display: flex;
   align-items: center;
   gap: 8px;
-  margin: 0;
   font-size: 15px;
   font-weight: 700;
   color: var(--color-accent);
   letter-spacing: -0.01em;
 }
 
+.landing-brand h1 {
+  margin: 0;
+  font-size: inherit;
+  font-weight: inherit;
+  color: inherit;
+  letter-spacing: inherit;
+}
+
 .landing-brand img {
   width: 24px;
   height: 24px;