fix: install libgomp1 + libgfortran5 so the prebuilt llama-cpp wheel can load

The Space was failing at runtime with:
RuntimeError: Failed to load shared library
'/usr/local/lib/python3.11/site-packages/llama_cpp/lib/llama.so'

The prebuilt llama-cpp-python CPU wheel ships libllama.so, which
dynamically links against:
- libgomp.so.1 (OpenMP runtime)
- libgfortran.so.5 (Fortran runtime)

Neither of these is present in the python:3.11-slim base image, so
dlopen() fails the moment we construct the Llama() object. The
previous error-surfacing work surfaced this exact failure to the
status line (no more generic 'model not loaded'), which made the
root cause obvious.

Fix: apt-get install libgomp1 libgfortran5 in the Dockerfile. Also
keep cmake + build-essential as a safety net so pip can fall back
to a source build if the prebuilt wheel is ever unavailable for the
exact Python version. --prefer-binary is kept so we still use the
fast prebuilt wheel by default.

Tests (host Python, not Docker): 12 unit + 42 E2E + 12 verify_llm_status
all pass. The Docker fix will take effect on the next Space rebuild.

Dockerfile

@@ -2,13 +2,26 @@ FROM python:3.11-slim
 
 WORKDIR /app
 
-# Install git for hf_hub_download and curl for health checks
-RUN apt-get update && apt-get install -y \
+# System dependencies:
+#   - git, curl                 : hf_hub_download + health checks
+#   - libgomp1, libgfortran5    : OpenMP + Fortran runtimes required by
+#                                 the prebuilt llama-cpp-python wheel's
+#                                 libllama.so (NOT in the slim base image;
+#                                 without these you get
+#                                 "Failed to load shared library ... libgomp.so.1")
+#   - cmake, build-essential     : safety net so pip can build llama-cpp-python
+#                                 from source if the prebuilt wheel is ever
+#                                 unavailable for this Python version
+RUN apt-get update && apt-get install -y --no-install-recommends \
     git \
     curl \
+    libgomp1 \
+    libgfortran5 \
+    cmake \
+    build-essential \
     && rm -rf /var/lib/apt/lists/*
 
-# Copy requirements and install Python deps (uses prebuilt llama-cpp-python wheel)
+# Copy requirements and install Python deps (prefer prebuilt llama-cpp-python wheel)
 COPY requirements.txt .
 RUN pip install --no-cache-dir --prefer-binary -r requirements.txt