Fix database not initializing in Docker (no db file created)

Root cause: DATABASE_URL used a relative path (file:./data/rackmapper.db).
Prisma CLI (migrate deploy) resolves relative SQLite paths from the
prisma/ schema directory -> /app/prisma/data/rackmapper.db, while the
Prisma Client at runtime resolves from CWD -> /app/data/rackmapper.db.
The migration ran against a different path than the bind mount, so no
database file ever appeared in /app/data (the mounted volume).

Fixes:
- Change DATABASE_URL to absolute path: file:/app/data/rackmapper.db
  everywhere (docker-compose, .env.example, UNRAID.md)
- Replace inline CMD with docker-entrypoint.sh:
    mkdir -p /app/data before migrating (safety net)
    npx prisma migrate deploy with set -e so failures are visible
    exec node dist/server/index.js
  This surfaces migration errors in docker logs instead of silently
  exiting, and ensures the data dir always exists before SQLite opens it
- Update .env.example to reflect plain ADMIN_PASSWORD and COOKIE_SECURE

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

UNRAID.md

@@ -109,7 +109,7 @@ Click **Add another Path, Port, Variable, Label or Device** → select **Variabl
 |---|---|---|
 | Node Environment | `NODE_ENV` | `production` |
 | Port | `PORT` | `3001` |
-| Database URL | `DATABASE_URL` | `file:./data/rackmapper.db` |
+| Database URL | `DATABASE_URL` | `file:/app/data/rackmapper.db` |
 | Admin Username | `ADMIN_USERNAME` | `admin` *(or your preferred username)* |
 | Admin Password | `ADMIN_PASSWORD` | `yourpassword` |
 | JWT Secret | `JWT_SECRET` | `a-long-random-string-min-32-chars` |
@@ -151,7 +151,7 @@ docker run -d \
   -v /mnt/user/appdata/rackmapper/data:/app/data \
   -e NODE_ENV=production \
   -e PORT=3001 \
-  -e DATABASE_URL="file:./data/rackmapper.db" \
+  -e DATABASE_URL="file:/app/data/rackmapper.db" \
   -e ADMIN_USERNAME=admin \
   -e ADMIN_PASSWORD=yourpassword \
   -e JWT_SECRET=a-long-random-string-min-32-chars \