chore: Add UI linter back (#3230)

# What does this PR do?

1. Adds `scripts/run-ui-linter.sh`
- Light script that checks whether `node_modules`,`eslint`, and
`prettier` exist before running linter
- When I introduced [the linter for the
UI](https://github.com/llamastack/llama-stack/pull/3156/files#diff-63a9c44a44acf85fea213a857769990937107cf072831e1a26808cfde9d096b9)
it forced the UI linter on all users, the small `node_modules` check
means that only users that have installed the UI locally (since
`node_modules` is in the gitignore) will actually end up having this
run. Additionally this does not do any install and just runs the
existing linter/prettier as requested by @mattf
2. Updates `.github/workflows/pre-commit.yml` to run CI again
- When I introduced the UI linter in the CI [in this
PR](https://github.com/llamastack/llama-stack/pull/3191) a failure
occurred because dependabot needed to be updated to also bump the
`package-lock.json` which was done [in this
PR](https://github.com/llamastack/llama-stack/pull/3212). All of this to
say, we shouldn't observe failures from dependabot again.
3. Updates `.pre-commit-config.yaml`
    - Calls `scripts/run-ui-linter.sh`

## AI Assistance Notice
I used Copilot minimally. 

## Test Plan
As
[requested](https://github.com/llamastack/llama-stack/pull/3207#discussion_r2288004872)
by @mattf I ran this after removing all of my `node_modules` and the
linter passed.

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

.github/workflows/pre-commit.yml

@@ -36,20 +36,16 @@ jobs:
             **/requirements*.txt
             .pre-commit-config.yaml
 
-      # npm ci may fail -
-      #   npm error `npm ci` can only install packages when your package.json and package-lock.json or npm-shrinkwrap.json are in sync. Please update your lock file with `npm install` before continuing.
-      #   npm error Invalid: lock file's llama-stack-client@0.2.17 does not satisfy llama-stack-client@0.2.18
+      - name: Set up Node.js
+        uses: actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af # v4.1.0
+        with:
+          node-version: '20'
+          cache: 'npm'
+          cache-dependency-path: 'llama_stack/ui/'
 
-      # - name: Set up Node.js
-      #   uses: actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af # v4.1.0
-      #   with:
-      #     node-version: '20'
-      #     cache: 'npm'
-      #     cache-dependency-path: 'llama_stack/ui/'
-
-      # - name: Install npm dependencies
-      #   run: npm ci
-      #   working-directory: llama_stack/ui
+      - name: Install npm dependencies
+        run: npm ci
+        working-directory: llama_stack/ui
 
       - uses: pre-commit/action@2c7b3805fd2a0fd8c1884dcaebf91fc102a13ecd # v3.0.1
         continue-on-error: true