docs: GEO-1125 Announcement diagrams

.diagrams/architecture/announcements/states.mermaid

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+---
+config:
+  layout: elk
+  elk:
+    nodePlacementStrategy: NETWORK_SIMPLEX
+---
+flowchart TD
+    draft>draft]
+    published>published]
+    expired>expired]
+    archived>archived]
+
+    published --Save as--> published
+    expired & draft --Save as--> draft & published
+    published -.On<br>expires_on<br>date.-> expired
+    draft & published & expired --Archive--> archived
+    archived & expired -.Scheduled<br>task.-> delete[Delete after 90 days]
+    published --Unpublish--> draft

.diagrams/architecture/announcements/user-actions.mermaid

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+flowchart TD
+    start([Admin User])
+
+    %% Nodes - Actions
+    active[Publicly available]
+    email[Send email 14 days before expire_on date]
+    scheduleExpire[Automatically expire announcement after expire_on date]
+    scheduleDelete[Automatically delete announcement after 90 days]
+
+    %% Nodes - decisions
+    choice{Actions}
+    saveAny{Save As}
+    saveP{Save As}
+
+    %% Nodes - Data objects
+    draft>fa:fa-file Draft Announcement]
+    published>fa:fa-file Published Announcement]
+    expired>fa:fa-file Expired Announcement]
+    archive>fa:fa-file Archived Announcement]
+
+    %% New workflow
+    start --> choice
+    choice --New--> saveAny
+
+    %% Existing workflows
+    choice --Edit draft/expired--> saveAny
+    choice --Edit published--> saveP
+    choice --Unpublish--> draft
+    published -.Scheduled task.-> email
+
+    %% Saving workflow
+    saveAny --Draft--> draft
+    saveAny & saveP --Publish--> published
+    published -.After active_on date.-> active
+
+    %% Expire workflows
+    published -.Scheduled task.-> scheduleExpire
+    scheduleExpire --> expired
+
+    %% Delete workflows
+    choice --Archive--> archive
+    expired & archive -.Scheduled task.-> scheduleDelete