secret-distribution: verify against live-checked KB, fix diagram, add real evidence

Source Trilium note (Secret Distribution Model) was live-verified and
stamped this session - Certificate Flow, App Secret Flow, Configuration
Distribution Flow, and the technitium_api_token Vault-KV exception all
confirmed against the real hosts, not just trusted from the KB.

Replaced the Mermaid diagram, which incorrectly showed the Configuration
Distribution Flow feeding into Vault directly, with a corrected version:
that flow is a control-plane gate on what Vault Agent renders, not a
peer data flow. Added a real Vault Agent log excerpt proving the full
redeploy chain (restart -> render -> reload_command -> container
recreated) actually happens, and restored the technitium_api_token
exception that was in the source note but missing from this doc.

assets/secret-distribution-flows.svg

@@ -0,0 +1,4 @@
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