docs: add AI generated visual architecture diagrams (#17)

* fix: enable use-recent-api-versions bicep lint rule

- Change use-recent-api-versions from off to warning in bicepconfig.json
- Warning (not error) avoids a first-time hard-fail surface since there is
  no CI gate yet to enforce it

* chore: ignore az bicep build output (infra/main.json)

- az bicep build --file infra/main.bicep emits a compiled ARM template
  that was previously untracked; ignore it as generated build output

* docs: add AI generated visual architecture diagrams

---------

Co-authored-by: Kim Harjamäki <kim.harjamaki@prosimo.fi>

Author: OgeonX-Ai

docs/architecture.md

@@ -4,6 +4,8 @@ The CAS Platform infrastructure relies on a modular, subscription-scoped orchest
 
 ## System Architecture Diagram
 
+![Visual Diagram](assets/cas_platform_architecture.png)
+
 ```mermaid
 flowchart TD
     subgraph Subscription ["Azure Subscription"]