Refactor constants management to use Pydantic BaseModel for configuration

- Replaced module-level path variables in constants.py with a structured Pydantic Config class.
- Updated all relevant modules (train.py, augmentation.py, exports.py, dataset-visualiser.py, manual_run.py) to access paths through the new config structure.
- Fixed bugs related to image processing and model saving.
- Enhanced test infrastructure to accommodate the new configuration approach.

This refactor improves code maintainability and clarity by centralizing configuration management.

scripts/run-performance-tests.sh

@@ -0,0 +1,64 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+RESULTS_DIR="$PROJECT_ROOT/test-results"
+
+cleanup() {
+  if [ -d "$RESULTS_DIR" ]; then
+    echo "Results saved to $RESULTS_DIR"
+  fi
+}
+trap cleanup EXIT
+
+mkdir -p "$RESULTS_DIR"
+
+echo "════════════════════════════════════"
+echo " Performance Tests"
+echo "════════════════════════════════════"
+echo ""
+echo "Thresholds (from test spec):"
+echo "  PT-AUG-01  Augmentation 10 images   ≤ 60s"
+echo "  PT-AUG-02  Parallel speedup          ≥ 1.5×"
+echo "  PT-DSF-01  Dataset formation 100 img  ≤ 30s"
+echo "  PT-ENC-01  Encrypt/decrypt 10MB       ≤ 5s"
+echo "  PT-INF-01  ONNX inference single      ≤ 10s"
+echo ""
+
+cd "$PROJECT_ROOT"
+
+FAILED=0
+
+if python -m pytest tests/performance/ \
+  --tb=short \
+  --junitxml="$RESULTS_DIR/performance-results.xml" \
+  -v; then
+  echo ""
+  echo "✓ All performance thresholds met"
+else
+  echo ""
+  echo "✗ Some performance thresholds exceeded"
+  FAILED=1
+fi
+
+echo ""
+echo "════════════════════════════════════"
+echo " Summary"
+echo "════════════════════════════════════"
+
+if [ -f "$RESULTS_DIR/performance-results.xml" ]; then
+  python -c "
+import xml.etree.ElementTree as ET
+t = ET.parse('$RESULTS_DIR/performance-results.xml').getroot()
+print(f\"Tests: {t.get('tests',0)}  Failures: {t.get('failures',0)}  Errors: {t.get('errors',0)}\")
+" 2>/dev/null || echo "Could not parse performance results XML"
+fi
+
+if [ $FAILED -ne 0 ]; then
+  echo "EXIT: 1 (thresholds exceeded)"
+  exit 1
+fi
+
+echo "EXIT: 0 (all thresholds met)"
+exit 0