fix: tune log levels across workspace — demote noisy warn to debug/trace

Reduce log noise for non-critical operational paths: connection retries,
expected fallbacks, graceful degradation, and optional feature absence.
Keeps warn/error for genuine failures requiring attention.

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

crates/risk-data/src/limits.rs

@@ -412,7 +412,7 @@ impl LimitsRepositoryImpl {
             | LimitType::VarLimit
             | LimitType::ConcentrationLimit
             | LimitType::LeverageLimit => {
-                tracing::error!("Unknown limit type in exposure calculation - using current value as conservative fallback");
+                tracing::warn!("Unknown limit type in exposure calculation - using current value as conservative fallback");
                 current_exposure.current_value // Conservative fallback for unknown limit types
             },
         };