fix: singing bowls ambient + Next.js 16 async params/cookies

Ambient:
- Replace oscillator drone/melody with singing bowl synthesis
- Each bowl: instant attack + exponential decay (7–12s) = real physical sound
- Two detuned copies per strike for natural shimmer beat
- A-minor pentatonic (A3 C4 D4 E4 G4 A4 C5 E5), weighted toward warm lows
- 30% chance of soft harmonic fifth companion tone per strike
- Random gaps 3–8s between strikes so it breathes naturally
- Two long hall reverb tails (2.4s / 4.8s) for warmth and space
- Graceful 2.5s fade-out on stop

Next.js 16 compatibility (breaking changes from v14→v16):
- Dynamic route params now Promise<{...}> → await params in all handlers
- cookies() now returns Promise → isAdmin() made async, await cookies()
- Files: [...path], memories/[id], media/[id], auth, upload all updated

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

src/app/api/memories/route.ts

@@ -1,15 +1,5 @@
 import { NextRequest, NextResponse } from 'next/server'
 import { getDb } from '@/lib/db'
-import { cookies } from 'next/headers'
-import { createHash } from 'crypto'
-
-function isAdmin() {
-  const token = cookies().get('admin_auth')?.value
-  const expected = createHash('sha256')
-    .update(process.env.ADMIN_PASSWORD || 'change-me')
-    .digest('hex')
-  return token === expected
-}
 
 export async function GET() {
   const db = getDb()