fix(security): harden public CV edges

JobTrackerApi/Services/RateLimitPartitionKeys.cs

@@ -0,0 +1,13 @@
+using Microsoft.AspNetCore.Http;
+
+namespace JobTrackerApi.Services;
+
+public static class RateLimitPartitionKeys
+{
+    public static string PublicPdf(HttpContext context)
+    {
+        var client = context.Connection.RemoteIpAddress?.ToString() ?? "unknown";
+        var slug = context.Request.RouteValues["slug"]?.ToString() ?? "unknown";
+        return $"public-pdf:{client}:{slug}";
+    }
+}