feat: bake iac_source_catalog into Docker image; fix YAML smoke test; add .gitignore

- Dockerfile: COPY iac_source_catalog.json in builder + final stage
- push_catalogs.sh: cp iac_source_catalog.json to iLSP repo root before SCP
- smoke_test_completions.py: detect WS CLOSE in _recv_until_id; 20s YAML init timeout; clearer error message
- .gitignore: standard Python exclusions

Fixes: iac_source_modules=0 (was never baked into image)

Dockerfile

@@ -21,6 +21,7 @@ COPY pyproject.toml .
 COPY ilsp/ ilsp/
 COPY bicep_modules_catalog.json .
 COPY pipeline_templates_catalog.json .
+COPY iac_source_catalog.json .
 
 RUN pip install --upgrade pip build \
     && python -m build --wheel --outdir /dist
@@ -45,6 +46,7 @@ COPY --from=bicep-downloader /opt/bicep-langserver /opt/bicep-langserver
 COPY --from=builder /dist/*.whl /tmp/
 COPY --from=builder /build/bicep_modules_catalog.json /bicep_modules_catalog.json
 COPY --from=builder /build/pipeline_templates_catalog.json /pipeline_templates_catalog.json
+COPY --from=builder /build/iac_source_catalog.json /iac_source_catalog.json
 RUN pip3 install --no-cache-dir --break-system-packages /tmp/*.whl && rm /tmp/*.whl
 
 # Configuration defaults (override via Nomad env)