build: add node-gyp for native module rebuilds (#15396)

# Overview

Adds `node-gyp` as a devDependency to enable native module compilation
on Node versions without prebuilt binaries.

## Key Changes

- Added `node-gyp@12.2.0` to root devDependencies

When `better-sqlite3` lacks prebuilt binaries (e.g., Node 24),
`prebuild-install` falls back to `node-gyp rebuild`. Without node-gyp
available, `pnpm install` fails with `ELIFECYCLE`.

## Design Decisions

Project-local over global: Adding node-gyp as a devDependency ensures
it's in `node_modules/.bin` during lifecycle scripts, avoiding reliance
on global installations. This is the standard approach for monorepos
with native dependencies.

Workaround for fresh clones:
```bash
pnpm install --ignore-scripts
pnpm rebuild
```