Remove all fallbacks: show errors, draw debug lines on calibration

- Remove try-except in CameraCalibrator — errors propagate to UI
- Remove auto-load of saved calibrations — always start uncalibrated
- Remove hardcoded "Base Setup" card with fake values
- Remove addStereocameras/getCamParams dead code
- Draw all detected Hough lines + corners on debug frame during calibration
- Show debug images in calibration tab after attempt
- Show error messages in UI instead of swallowing them

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/web/app.py

@@ -112,11 +112,16 @@ def api_calibration_trigger():
     if fn is None:
         return jsonify({'ok': False, 'error': 'Calibration not available'}), 500
 
+    import traceback
     try:
         result = fn()
-        return jsonify({'ok': True, 'result': result})
+        # Check if any camera failed
+        any_ok = any(r.get('ok') for r in result.values())
+        return jsonify({'ok': any_ok, 'result': result})
     except Exception as e:
-        return jsonify({'ok': False, 'error': str(e)}), 500
+        tb = traceback.format_exc()
+        print(f"[CALIBRATION ERROR]\n{tb}")
+        return jsonify({'ok': False, 'error': f'{type(e).__name__}: {e}'}), 500
 
 
 @app.route('/api/calibration/data')