chore(tooling): switch to fnm + pnpm, add DEPLOYMENT.md

Pin Node 24 via .node-version/.nvmrc and pnpm 9.15.0 via
package.json#packageManager. Regenerate lockfile as pnpm-lock.yaml.
Rewrite README setup + scripts table around pnpm, and add a
production deployment guide covering systemd, nginx, upgrades,
rollback, and backups.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

drizzle/README.md

@@ -5,10 +5,10 @@ TypeScript schema in `src/lib/server/db/schema/`.
 
 Commands:
 
-- `npm run db:generate` — diff the schema vs. the latest snapshot and emit a new `.sql` file
-- `npm run db:migrate` — apply pending migrations to `DATABASE_URL`
-- `npm run db:push` — skip migrations and sync the schema directly (**dev only**)
-- `npm run db:studio` — open the Drizzle Studio UI
+- `pnpm run db:generate` — diff the schema vs. the latest snapshot and emit a new `.sql` file
+- `pnpm run db:migrate` — apply pending migrations to `DATABASE_URL`
+- `pnpm run db:push` — skip migrations and sync the schema directly (**dev only**)
+- `pnpm run db:studio` — open the Drizzle Studio UI
 
 After every generate, review the SQL for surprises — especially around: