fix(ci): remove broken requirements-lock.txt dependency installation

The requirements-lock.txt was generated with non-existent Python 3.14 and
contains fictitious package versions (e.g., numpy 2.3.5, torch 2.9.1) that
don't exist on PyPI.

For a syntax check job, installing heavy ML dependencies is unnecessary.
The compileall module only needs Python standard library to verify syntax.

This change:
- Removes pip install step from Python syntax check job
- Removes pip caching (not needed without pip install)
- Keeps only the byte-compile syntax verification step

Author: aviralgarg05

.github/workflows/ci.yml

@@ -85,11 +85,6 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: "3.10"
-          cache: "pip"
-          cache-dependency-path: nexum_ai/requirements-lock.txt
 
-      - name: Install dependencies
-        run: pip install -r nexum_ai/requirements-lock.txt
-
-      - name: Byte-compile nexum_ai
-        run: python -m compileall nexum_ai
+      - name: Byte-compile nexum_ai (syntax check)
+        run: python -m compileall -q nexum_ai