chore: add Biome for formatting and linting (#116)

- Add Biome as formatter and linter (replaces Prettier)
- Configure Husky + lint-staged for pre-commit hooks
- Add VS Code settings for format on save
- Ignore components/ui/ (shadcn generated code)
- Remove semicolons, use 4-space indent
- Reformat all files to new style

app/api/log-save/route.ts

@@ -1,65 +1,71 @@
-import { getLangfuseClient } from '@/lib/langfuse';
-import { randomUUID } from 'crypto';
-import { z } from 'zod';
+import { randomUUID } from "crypto"
+import { z } from "zod"
+import { getLangfuseClient } from "@/lib/langfuse"
 
 const saveSchema = z.object({
-  filename: z.string().min(1).max(255),
-  format: z.enum(['drawio', 'png', 'svg']),
-  sessionId: z.string().min(1).max(200).optional(),
-});
+    filename: z.string().min(1).max(255),
+    format: z.enum(["drawio", "png", "svg"]),
+    sessionId: z.string().min(1).max(200).optional(),
+})
 
 export async function POST(req: Request) {
-  const langfuse = getLangfuseClient();
-  if (!langfuse) {
-    return Response.json({ success: true, logged: false });
-  }
-
-  // Validate input
-  let data;
-  try {
-    data = saveSchema.parse(await req.json());
-  } catch {
-    return Response.json({ success: false, error: 'Invalid input' }, { status: 400 });
-  }
-
-  const { filename, format, sessionId } = data;
-
-  try {
-    const timestamp = new Date().toISOString();
-
-    // Find the most recent chat trace for this session to attach the save flag
-    const tracesResponse = await langfuse.api.trace.list({
-      sessionId,
-      limit: 1,
-    });
-
-    const traces = tracesResponse.data || [];
-    const latestTrace = traces[0];
-
-    if (latestTrace) {
-      // Add a score to the existing trace to flag that user saved
-      await langfuse.api.ingestion.batch({
-        batch: [
-          {
-            type: 'score-create',
-            id: randomUUID(),
-            timestamp,
-            body: {
-              id: randomUUID(),
-              traceId: latestTrace.id,
-              name: 'diagram-saved',
-              value: 1,
-              comment: `User saved diagram as ${filename}.${format}`,
-            },
-          },
-        ],
-      });
+    const langfuse = getLangfuseClient()
+    if (!langfuse) {
+        return Response.json({ success: true, logged: false })
     }
-    // If no trace found, skip logging (user hasn't chatted yet)
 
-    return Response.json({ success: true, logged: !!latestTrace });
-  } catch (error) {
-    console.error('Langfuse save error:', error);
-    return Response.json({ success: false, error: 'Failed to log save' }, { status: 500 });
-  }
+    // Validate input
+    let data
+    try {
+        data = saveSchema.parse(await req.json())
+    } catch {
+        return Response.json(
+            { success: false, error: "Invalid input" },
+            { status: 400 },
+        )
+    }
+
+    const { filename, format, sessionId } = data
+
+    try {
+        const timestamp = new Date().toISOString()
+
+        // Find the most recent chat trace for this session to attach the save flag
+        const tracesResponse = await langfuse.api.trace.list({
+            sessionId,
+            limit: 1,
+        })
+
+        const traces = tracesResponse.data || []
+        const latestTrace = traces[0]
+
+        if (latestTrace) {
+            // Add a score to the existing trace to flag that user saved
+            await langfuse.api.ingestion.batch({
+                batch: [
+                    {
+                        type: "score-create",
+                        id: randomUUID(),
+                        timestamp,
+                        body: {
+                            id: randomUUID(),
+                            traceId: latestTrace.id,
+                            name: "diagram-saved",
+                            value: 1,
+                            comment: `User saved diagram as ${filename}.${format}`,
+                        },
+                    },
+                ],
+            })
+        }
+        // If no trace found, skip logging (user hasn't chatted yet)
+
+        return Response.json({ success: true, logged: !!latestTrace })
+    } catch (error) {
+        console.error("Langfuse save error:", error)
+        return Response.json(
+            { success: false, error: "Failed to log save" },
+            { status: 500 },
+        )
+    }
 }