feat(#28): add ServiceRegistry — centralise enrichment/classify/dedup/sort pipeline

[longieirl]

Summary

Introduces `ServiceRegistry` as the single wiring point for all transaction processing services (enrichment, classification, duplicate detection, sorting). Consolidates logic that was previously spread across `BankStatementProcessor` and `TransactionProcessingOrchestrator`, and trims the orchestrator to IBAN grouping only.

Changes

• Add `services/service_registry.py` — `_ServiceContext` dataclass + `ServiceRegistry` class with `from_config()` factory, `process_transaction_group()`, `group_by_iban()`, and escape-hatch getters
• Wire `processor.py` to use `self._registry.process_transaction_group()` and `self._registry.group_by_iban()`
• Update `ProcessorFactory.create_custom` and `BankStatementProcessorBuilder.build()` to construct `ServiceRegistry` and inject via `registry=` kwarg
• Trim `TransactionProcessingOrchestrator` to `group_by_iban` only — enrichment/classification/dedup/sort moved to `ServiceRegistry`
• Fix wrong import of `ChronologicalSortingStrategy` (`patterns.strategies` → `services.sorting_service`)
• Add `tests/services/test_service_registry.py` (boundary tests: `from_config` wiring, pipeline, delegation, escape hatches)
• Trim `test_transaction_processing_orchestrator.py` to `group_by_iban` delegation test only

Note: `TransactionProcessingOrchestrator` is retained for backward compatibility — a follow-up issue will track its complete removal.

Type

• New feature
• Refactoring

Testing

• Tests pass (coverage ≥ 91%)
• Manually tested

Checklist

• Code follows project style
• Self-reviewed
• Documentation updated (if needed)
• No new warnings