feat: Settings page, DELETE traces endpoint, Anthropic SDK, dashboard bug fixes

- Add /dashboard/settings with SDK connection details, data stats, purge
- Add DELETE /api/traces/[id] with cascade deletion
- Add Anthropic integration (wrap_anthropic) for Python SDK
- Fix missing root duration (totalDuration -> durationMs mapping)
- Fix truncated JSON in decision tree nodes (extract readable labels)
- Fix hardcoded 128K maxTokens in token gauge (model-aware context windows)
- Enable Settings nav item in sidebar

apps/web/src/components/trace-analytics.tsx

@@ -461,13 +461,35 @@ function CostBreakdown({
 // Section C: Token Usage Gauge
 function TokenUsageGauge({ trace }: { trace: Trace }) {
   const tokenData = useMemo(() => {
-    // Try to get total tokens from various sources
     const totalTokens =
       (trace.metadata?.totalTokens as number | null | undefined) ??
       (trace.metadata?.tokenCount as number | null | undefined) ??
       null;
 
-    const maxTokens = 128000; // Default context window
+    const modelContextWindows: Record<string, number> = {
+      "gpt-4": 8192,
+      "gpt-4-32k": 32768,
+      "gpt-4-turbo": 128000,
+      "gpt-4o": 128000,
+      "gpt-4o-mini": 128000,
+      "gpt-3.5-turbo": 16385,
+      "claude-3-opus": 200000,
+      "claude-3-sonnet": 200000,
+      "claude-3-haiku": 200000,
+      "claude-3.5-sonnet": 200000,
+      "claude-4-opus": 200000,
+      "claude-4-sonnet": 200000,
+    };
+
+    const model = (trace.metadata?.model as string | undefined) ?? "";
+    const modelLower = model.toLowerCase();
+    let maxTokens = 128000;
+    for (const [prefix, ctx] of Object.entries(modelContextWindows)) {
+      if (modelLower.startsWith(prefix)) {
+        maxTokens = ctx;
+        break;
+      }
+    }
 
     return {
       totalTokens,