fix: resolve Docker Compose build failure with Prisma Client generation

Fix critical issue where `docker compose build` was failing with:
"Module not found: Can't resolve '../prisma/client-generated'"

Root cause:
- Next.js build requires Prisma Client during webpack compilation
- Prisma Client was not being generated before the Next.js build step

Changes:
1. keep-notes/Dockerfile:
   - Add explicit `RUN npx prisma generate` in builder stage before `npm run build`
   - Ensures client-generated directory exists when Next.js compiles

2. keep-notes/package.json:
   - Update build script: "prisma generate && next build --webpack"
   - Double-protection: runs prisma generate both in Dockerfile and build script

3. docker-compose.yml:
   - Remove obsolete `version: '3.8'` attribute (deprecated in Docker Compose v2)

Result:
✓ Docker build now completes successfully
✓ Prisma Client generated at ./prisma/client-generated
✓ Next.js webpack compilation finds the client module

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

docker-compose.yml

@@ -1,5 +1,3 @@
-version: '3.8'
-
 services:
   # ============================================
   # keep-notes - Next.js Web Application