docs: update Node.js to 24 LTS, switch to nvm + corepack

- Use nvm v0.40.4 + nvm install 24 (24.14.0 LTS) instead of nodesource
- Use corepack enable pnpm instead of npm install -g pnpm
- Add symlink step: ln -sf \$(nvm which current) /usr/local/bin/node so
  systemd service can reference a stable path
- Update ExecStart in innercontext-node.service: /usr/bin → /usr/local/bin
- Update Node.js version references in README.md (22 → 24 LTS)

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

README.md

@@ -33,7 +33,7 @@ API docs available at `http://localhost:8000/docs`.
 
 ## Frontend quick start
 
-**Requirements:** Node.js 22+, [pnpm](https://pnpm.io/)
+**Requirements:** Node.js 24 LTS+, [pnpm](https://pnpm.io/)
 
 ```bash
 cd frontend

docs/DEPLOYMENT.md

@@ -64,12 +64,19 @@ curl -LsSf https://astral.sh/uv/install.sh | sh
 source $HOME/.local/bin/env   # or re-login
 ```
 
-### Node.js 22 + pnpm
+### Node.js 24 LTS + pnpm
 
 ```bash
-curl -fsSL https://deb.nodesource.com/setup_22.x | bash -
-apt install -y nodejs
-npm install -g pnpm
+curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.4/install.sh | bash
+. "$HOME/.nvm/nvm.sh"
+nvm install 24
+corepack enable pnpm
+```
+
+Create a stable symlink so systemd can find `node` at a fixed path:
+
+```bash
+ln -sf "$(nvm which current)" /usr/local/bin/node
 ```
 
 ### Application user

systemd/innercontext-node.service

@@ -10,7 +10,7 @@ WorkingDirectory=/opt/innercontext/frontend
 Environment=PORT=3000
 Environment=HOST=127.0.0.1
 EnvironmentFile=/opt/innercontext/frontend/.env.production
-ExecStart=/usr/bin/node /opt/innercontext/frontend/build/index.js
+ExecStart=/usr/local/bin/node /opt/innercontext/frontend/build/index.js
 Restart=on-failure
 RestartSec=5