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/api/memories/route.ts

@@ -20,11 +20,7 @@ export async function GET() {
 }
 
 export async function POST(req: NextRequest) {
-  if (!isAdmin()) {
-    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
-  }
-
-  const { title, content } = await req.json()
+  const { title, content, author } = await req.json()
   if (!title?.trim() || !content?.trim()) {
     return NextResponse.json(
       { error: 'Titel und Inhalt sind erforderlich' },
@@ -34,8 +30,8 @@ export async function POST(req: NextRequest) {
 
   const db = getDb()
   const result = db
-    .prepare('INSERT INTO memories (title, content) VALUES (?, ?)')
-    .run(title.trim(), content.trim())
+    .prepare('INSERT INTO memories (title, content, author) VALUES (?, ?, ?)')
+    .run(title.trim(), content.trim(), author?.trim() || null)
   const memory = db
     .prepare('SELECT * FROM memories WHERE id = ?')
     .get(result.lastInsertRowid)