docs(timeline): register timeline domain in package tables and diagrams

Add timeline/ to the root and backend package tables, TimelineEvent to the
domain-model entity tables, TimelineEvent/EventType/Zeitstrahl to the
glossary, a new l3-backend-timeline C4 component diagram, and the
timeline_events table + two join tables (with their CHECKs and cascade FKs)
to the db-orm and db-relationships ER diagrams. Bumps the db-orm snapshot to
V77.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/architecture/db/db-orm.puml

@@ -1,6 +1,6 @@
 @startuml db-orm
-' Schema source: Flyway V1–V76 (excl. V37, V43 — intentionally removed)
-' Schema as of:  V76 (2026-06-12)
+' Schema source: Flyway V1–V77 (excl. V37, V43 — intentionally removed)
+' Schema as of:  V77 (2026-06-12)
 ' ⚠ This is a versioned snapshot. Update when the schema changes significantly.
 
 hide circle
@@ -386,6 +386,39 @@ package "Supporting" {
   }
 }
 
+' ── Timeline (Zeitstrahl) ──
+package "Timeline" {
+
+  entity timeline_events {
+    id : UUID <<PK>>
+    --
+    title : VARCHAR(255) NOT NULL
+    type : VARCHAR(16) NOT NULL
+    event_date : DATE NOT NULL
+    date_precision : VARCHAR(16) NOT NULL DEFAULT 'YEAR'
+    event_date_end : DATE
+    description : TEXT
+    created_by : UUID NOT NULL
+    created_at : TIMESTAMP
+    updated_by : UUID NOT NULL
+    updated_at : TIMESTAMP
+    version : BIGINT
+    ==
+    CHECK ((date_precision = 'RANGE') = (event_date_end IS NOT NULL))
+    CHECK (date_precision <> 'UNKNOWN')
+  }
+
+  entity timeline_event_persons {
+    timeline_event_id : UUID <<FK>>
+    person_id : UUID <<FK>>
+  }
+
+  entity timeline_event_documents {
+    timeline_event_id : UUID <<FK>>
+    document_id : UUID <<FK>>
+  }
+}
+
 ' Auth relationships
 app_users_groups }o--|| app_users : app_user_id
 app_users_groups }o--|| user_groups : group_id
@@ -449,4 +482,10 @@ geschichten_persons }o--|| persons : person_id
 journey_items }o--|| geschichten : geschichte_id (ON DELETE CASCADE)
 journey_items }o--o| documents : document_id (ON DELETE SET NULL)
 
+' Timeline relationships
+timeline_event_persons }o--|| timeline_events : timeline_event_id (ON DELETE CASCADE)
+timeline_event_persons }o--|| persons : person_id (ON DELETE CASCADE)
+timeline_event_documents }o--|| timeline_events : timeline_event_id (ON DELETE CASCADE)
+timeline_event_documents }o--|| documents : document_id (ON DELETE CASCADE)
+
 @enduml