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.

.cursor/skills/refactor/phases/00-baseline.md

@@ -0,0 +1,40 @@
+# Phase 0: Context & Baseline
+
+**Role**: Software engineer preparing for refactoring
+**Goal**: Collect refactoring goals and capture baseline metrics
+**Constraints**: Measurement only — no code changes
+
+## 0a. Collect Goals
+
+If PROBLEM_DIR files do not yet exist, help the user create them:
+
+1. `problem.md` — what the system currently does, what changes are needed, pain points
+2. `acceptance_criteria.md` — success criteria for the refactoring
+3. `security_approach.md` — security requirements (if applicable)
+
+Store in PROBLEM_DIR.
+
+## 0b. Capture Baseline
+
+1. Read problem description and acceptance criteria
+2. Measure current system metrics using project-appropriate tools:
+
+| Metric Category | What to Capture |
+|----------------|-----------------|
+| **Coverage** | Overall, unit, blackbox, critical paths |
+| **Complexity** | Cyclomatic complexity (avg + top 5 functions), LOC, tech debt ratio |
+| **Code Smells** | Total, critical, major |
+| **Performance** | Response times (P50/P95/P99), CPU/memory, throughput |
+| **Dependencies** | Total count, outdated, security vulnerabilities |
+| **Build** | Build time, test execution time, deployment time |
+
+3. Create functionality inventory: all features/endpoints with status and coverage
+
+**Self-verification**:
+- [ ] All metric categories measured (or noted as N/A with reason)
+- [ ] Functionality inventory is complete
+- [ ] Measurements are reproducible
+
+**Save action**: Write `REFACTOR_DIR/baseline_metrics.md`
+
+**BLOCKING**: Present baseline summary to user. Do NOT proceed until user confirms.