fix: libgles2/libegl1 in Dockerfile + handle missing mp.solutions namespace

Two runtime errors observed on the live Space:
1. libGLESv2.so.2 missing — added libgles2 + libegl1 to apt-get install.
MediaPipe needs both the OpenGL and OpenGL ES variants on Linux.
2. AttributeError: module 'mediapipe' has no attribute 'solutions' —
MediaPipe 0.10.15+ deprecated the legacy `mp.solutions` namespace; the
Holistic solution moved to mediapipe-extended. Production fingerspelling
already uses the Tasks API (signbridge.recognizer.landmark_classifier),
so the Holistic-based pose-debug overlay is now optional. landmarks.py
handles the missing namespace gracefully — logs and returns early
instead of crashing the Space's import path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -5,6 +5,8 @@ FROM python:3.11-slim
 RUN apt-get update && apt-get install -y --no-install-recommends \
     git \
     libgl1 \
+    libgles2 \
+    libegl1 \
     libglib2.0-0 \
     libsm6 \
     libxext6 \

signbridge/recognizer/landmarks.py

@@ -40,8 +40,20 @@ class LandmarkExtractor:
             import mediapipe as mp  # type: ignore[import-not-found]
         except ImportError:
             logger.warning(
-                "mediapipe not installed; landmarks will be all zeros. "
-                "Install via `pip install mediapipe>=0.10.18`."
+                "mediapipe not installed; landmarks will be all zeros."
+            )
+            return
+        # MediaPipe 0.10.15+ deprecated and eventually removed the legacy
+        # `mp.solutions` namespace in favour of `mp.tasks`. The Holistic
+        # solution moved to `mediapipe-extended` and isn't critical for the
+        # production fingerspelling path (that uses Tasks API in
+        # signbridge.recognizer.landmark_classifier). When `solutions` is
+        # missing we silently skip the pose-debug overlay rather than
+        # crashing the whole Space.
+        if not hasattr(mp, "solutions"):
+            logger.info(
+                "mediapipe.solutions not available (Holistic deprecated); "
+                "pose-tracking debug overlay disabled."
             )
             return
         self._mp_drawing = mp.solutions.drawing_utils