docs(timeline): RTM, CLAUDE.md, and C4 updates for #777 assembly endpoint

- Add 20 REQ-NNN rows for issue #777 (all Done) to .specify/rtm.md
- Update CLAUDE.md timeline package description with TimelineService/TimelineController
- Extend l3-backend-timeline.puml with TimelineService/TimelineController components
  and their edges to PersonService and DocumentService

Refs #777
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/architecture/c4/l3-backend-timeline.puml

@@ -9,11 +9,14 @@ System_Boundary(backend, "API Backend (Spring Boot)") {
     Component(timelineRepo, "TimelineEventRepository", "Spring Data JPA", "Reads and writes TimelineEvent rows and their persons/documents join tables (timeline_event_persons, timeline_event_documents).")
 
     Component(timelineSvc, "TimelineEventService", "Spring Service", "Owns curated-event CRUD: assembles TimelineEventView inside the transaction (lazy ManyToMany + open-in-view=false, ADR-036/ADR-040), populates createdBy/updatedBy from the session principal, and translates optimistic-lock conflicts to DomainException.conflict. Also exposes assembleDerivedEvents(): computes Geburt/Tod/Heirat TimelineEntryDTOs on read from Person/PersonRelationship data — never persisted (ADR-043).")
-    Component(timelineCtrl, "TimelineEventController", "Spring MVC", "Exposes /api/timeline reads (READ_ALL) and writes (WRITE_ALL). createdBy/updatedBy are never bound from request bodies (CWE-639).")
+    Component(timelineCtrl, "TimelineEventController", "Spring MVC", "Exposes /api/timeline/events reads (READ_ALL) and writes (WRITE_ALL). createdBy/updatedBy are never bound from request bodies (CWE-639).")
+
+    Component(timelineAssemblySvc, "TimelineService", "Spring Service", "Assembles GET /api/timeline response: merges curated TimelineEvent rows, derived life-events (via TimelineEventService), and archive letters (via DocumentService) into a year-bucketed TimelineDTO. Applies personId, generation, type, fromYear/toYear filters. WITHIN_BAND_ORDER: precision rank desc → date asc → title alpha → id tiebreak.")
+    Component(timelineAssemblyCtrl, "TimelineController", "Spring MVC", "Exposes GET /api/timeline (READ_ALL). Five optional query params: personId, generation (@Min(0)), type (EventType enum), fromYear, toYear. @Validated on class for constraint enforcement.")
 }
 
-System_Ext(documentDomain, "Document domain", "Provides DatePrecision (shared value type) and Document references for linked letters")
-System_Ext(personDomain, "Person domain", "Provides Person references (PersonService.findAllFamilyMembers) and SPOUSE_OF edges (RelationshipService.findAllSpouseEdges) for derived-event assembly and curated-event links")
+System_Ext(documentDomain, "Document domain", "Provides DatePrecision (shared value type), Document references for linked letters, and getAllForTimeline() bulk fetch")
+System_Ext(personDomain, "Person domain", "Provides Person references (PersonService.findAllFamilyMembers, getPersonsByGeneration, getById) and SPOUSE_OF edges (RelationshipService.findAllSpouseEdges) for derived-event assembly and generation filtering")
 
 Rel(timelineRepo, db, "SQL queries", "JDBC")
 Rel(timelineSvc, timelineRepo, "Reads / writes events")
@@ -21,5 +24,10 @@ Rel(timelineCtrl, timelineSvc, "Delegates to")
 Rel(timelineRepo, personDomain, "References persons via join table")
 Rel(timelineRepo, documentDomain, "References documents via join table")
 Rel(timelineSvc, personDomain, "findAllFamilyMembers() + findAllSpouseEdges() for derived-event assembly")
+Rel(timelineAssemblyCtrl, timelineAssemblySvc, "Delegates to")
+Rel(timelineAssemblySvc, timelineRepo, "findAll() for curated events")
+Rel(timelineAssemblySvc, timelineSvc, "assembleDerivedEvents() for derived life-events")
+Rel(timelineAssemblySvc, personDomain, "getPersonsByGeneration(), getById() for generation/personId filters")
+Rel(timelineAssemblySvc, documentDomain, "getAllForTimeline(), getDocumentsBySender(), getDocumentsByReceiver() for letter layer")
 
 @enduml