feat: implement Phase 4 endpoint dragging with visual handles

src/app/api/annotations/[id]/route.ts

@@ -3,6 +3,57 @@ import { db } from '@/lib/db';
 import { annotations } from '@/lib/db/schema';
 import { eq } from 'drizzle-orm';
 
+export async function PATCH(
+  request: NextRequest,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  try {
+    const { id: idParam } = await params;
+    const id = parseInt(idParam);
+
+    if (isNaN(id)) {
+      return NextResponse.json(
+        { error: 'Invalid annotation ID' },
+        { status: 400 }
+      );
+    }
+
+    const body = await request.json();
+    const { geometry } = body;
+
+    if (!geometry) {
+      return NextResponse.json(
+        { error: 'Geometry data is required' },
+        { status: 400 }
+      );
+    }
+
+    const result = await db
+      .update(annotations)
+      .set({ geometry: JSON.stringify(geometry) })
+      .where(eq(annotations.id, id))
+      .returning();
+
+    if (result.length === 0) {
+      return NextResponse.json(
+        { error: 'Annotation not found' },
+        { status: 404 }
+      );
+    }
+
+    const updated = result[0];
+    return NextResponse.json({
+      ...updated,
+      geometry: updated.geometry ? JSON.parse(updated.geometry as string) : null,
+    });
+  } catch (error: any) {
+    return NextResponse.json(
+      { error: error.message || 'Failed to update annotation' },
+      { status: 500 }
+    );
+  }
+}
+
 export async function DELETE(
   request: NextRequest,
   { params }: { params: Promise<{ id: string }> }