feat: dark cinematic hero + public memory write section

- HeroSection: animated warmgold/burgundy/indigo orbs on #060304 bg, film grain CSS overlay, larger glowing typography
- WriteSection: new public component – collapsible form (name optional, title, textarea) posts to /api/memories without auth, shows success state and refreshes page
- API: remove isAdmin() guard from POST /api/memories, accept author field
- DB: migration adds author TEXT column to memories (try/catch for existing DBs)
- Types: add author: string | null to Memory type
- MemorySection: display "— [Name]" beneath date when author is set
- globals.css: grain keyframe animation for film-texture overlay

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/app/page.tsx

@@ -4,6 +4,7 @@ import HeroSection from '@/components/HeroSection'
 import PhotoSlideshow from '@/components/PhotoSlideshow'
 import PhotoGallery from '@/components/PhotoGallery'
 import MemorySection from '@/components/MemorySection'
+import WriteSection from '@/components/WriteSection'
 import MusicPlayer from '@/components/MusicPlayer'
 import VideoGallery from '@/components/VideoGallery'
 
@@ -81,6 +82,9 @@ export default async function HomePage() {
         </section>
       )}
 
+      {/* Write section – public */}
+      <WriteSection />
+
       {/* Memories */}
       <MemorySection memories={memories} />