feat(settings): CEO display name is configurable, Renzo hardcode removed (#612)

The header chip and the Settings User Info card rendered a literal 'Renzo'.
The name now lives in the system_settings store under ceo_name (validated:
trimmed, non-empty, max 60 chars) with the same client-served default the
transcript-retention card uses, editable inline from the User Info card.
Agent prompts already refer to 'the CEO' generically, so no prompt rewiring;
the two agent-facing RAG docs drop the name too. License/CLA copyright is
untouched.

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

docs/rag/architecture/org-structure.md

@@ -3,7 +3,7 @@
 ## Hierarchy
 
 ```
-CEO (Renzo - Human)
+CEO (Human)
     |
     +-- Board (4 agents)
     |    +-- Product Owner

docs/rag/roles/ceo.md

@@ -2,7 +2,7 @@
 
 ## Identity
 
-- **Agent**: ceo (Renzo - Human)
+- **Agent**: ceo (Human)
 - **Role**: `ceo`
 - **Team**: board
 - **Reports to**: N/A (top of hierarchy)