feat: ESPI 4.0 Schema Compliance - Phase 25: EndDevice + DTO Cleanup (#94)

Phase 25: EndDevice Implementation + ESPI 4.0 DTO Cleanup

- Implemented EndDevice entity with full ESPI 4.0 XSD compliance
- Cleaned 13 DTOs (4 customer + 9 usage) - removed id/uuid fields
- Created 8 integration test files for Phases 18, 23, 24, 25
- Fixed NotificationMethodKind enum to match customer.xsd
- Fixed JAXB OffsetDateTime marshalling in LifecycleDateDto and AcceptanceTestDto
- All 654 unit tests + 99 integration tests passing

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: dfcoffin

CLAUDE.md

@@ -230,6 +230,10 @@ ESPI uses Atom XML feeds for data exchange. Key patterns:
 - All tests must pass before committing: `mvn test`
 - Run tests for affected module and its dependents: `mvn test -pl <module> -am`
 - Integration tests should pass before PR merge: `mvn verify -Pfull-integration`
+- **IMPORTANT**: Use AssertJ chained assertions - combine all assertions for a single object into one assertion chain
+  - Good: `assertThat(retrieved).isPresent().hasValueSatisfying(device -> assertThat(device).extracting(...).containsExactly(...))`
+  - Bad: Multiple separate `assertThat()` statements for the same object
+  - This improves readability and provides better failure messages
 
 ### Common Development Patterns