CELDEV-1351 Add Presentation REST API

[fpichler]

Summary

• add the reusable read-only Presentation REST metadata and batch-render endpoints
• preserve ordered rights-visible slides, legacy root IDs/classes, effective language, layouts, and controlled errors
• provide atomic rendering with full per-slide context isolation
• add component, web-context, OpenAPI, renderer-fidelity, security, and contract tests
• simplify redundant OpenAPI annotations while preserving the generated contract inferred from Spring request and response types
• align the new celements-presentation JAR and celements-presentation-web WAR with the 7.3 development line

Requirements

• CELDEV-1351

Depends on

• CELDEV-1351 Extract Presentation REST reuse seams celements-core#423

Validation

• presentation component tests: 45 passed
• real Spring component graph and anonymous method-security tests passed
• generated OpenAPI contract tests passed, including focused validation after annotation simplification
• real-renderer RichText/media/semantic output and atomicity tests passed
• isolated 7.3 component/WAR build and coordinated dependency chain passed
• Docker runtime: Spring/DispatcherServlet startup and anonymous controlled responses verified
• git diff --check

Representative successful presentation and authenticated-preview requests still require suitable runtime fixture data.