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/04-execution.md

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+# Phase 4: Execution
+
+**Role**: Software architect and developer
+**Goal**: Analyze coupling and execute decoupling changes
+**Constraints**: Small incremental changes; tests must stay green after every change
+
+## 4a. Analyze Coupling
+
+1. Analyze coupling between components/modules
+2. Map dependencies (direct and transitive)
+3. Identify circular dependencies
+4. Form decoupling strategy
+
+Write `REFACTOR_DIR/coupling_analysis.md`:
+- Dependency graph (Mermaid)
+- Coupling metrics per component
+- Problem areas: components involved, coupling type, severity, impact
+- Decoupling strategy: priority order, proposed interfaces/abstractions, effort estimates
+
+**BLOCKING**: Present coupling analysis to user. Do NOT proceed until user confirms strategy.
+
+## 4b. Execute Decoupling
+
+For each change in the decoupling strategy:
+
+1. Implement the change
+2. Run blackbox tests
+3. Fix any failures
+4. Commit with descriptive message
+
+Address code smells encountered: long methods, large classes, duplicate code, dead code, magic numbers.
+
+Write `REFACTOR_DIR/execution_log.md`:
+- Change description, files affected, test status per change
+- Before/after metrics comparison against baseline
+
+**Self-verification**:
+- [ ] All tests still pass after execution
+- [ ] No circular dependencies remain (or reduced per plan)
+- [ ] Code smells addressed
+- [ ] Metrics improved compared to baseline
+
+**Save action**: Write execution artifacts
+
+**BLOCKING**: Present execution summary to user. Do NOT proceed until user confirms.