feat(simulation): SQLite settings storage with IPC protocol v20 (#627)

Per-player settings via rusqlite (bundled, zero runtime dep). Server
owns the settings DB; client sends ChangeSettings commands over IPC.
Extensible key-value with typed columns (String/Int/Float/Bool).
Protocol bumped to v20 with settings_response in ObserverSnapshot.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/bridge/text_renderer.rs

@@ -319,6 +319,7 @@ mod tests {
             sim_errors: vec![],
             debug_response: None,
             current_ticker: None,
+            settings_response: None,
         }
     }
 
@@ -459,6 +460,7 @@ mod tests {
             sim_errors: vec![],
             debug_response: None,
             current_ticker: None,
+            settings_response: None,
         };
         let text = format_snapshot_text(&snap);
         assert!(text.contains("Tick 0"));