add csfloat api usage

BlueLaminate/BlueLaminate.Scraper/CsFloat/CsFloatRateLimit.cs

@@ -0,0 +1,33 @@
+namespace BlueLaminate.Scraper.CsFloat;
+
+/// <summary>
+/// Rate-limit state parsed from a CSFloat API response's headers. The official
+/// docs don't pin down the exact header names, so this is populated generically
+/// (any header whose name contains "ratelimit"/"rate-limit", plus "retry-after")
+/// and keeps the <see cref="Raw"/> map so the real names surface during the
+/// spike. A future catalog sweep uses <see cref="Remaining"/>/<see cref="Reset"/>
+/// to pace requests and avoid 429s.
+/// </summary>
+/// <param name="Limit">Max requests allowed in the current window, if reported.</param>
+/// <param name="Remaining">Requests left in the current window, if reported.</param>
+/// <param name="Reset">Raw reset value as sent (epoch seconds or seconds-until — unverified).</param>
+/// <param name="RetryAfter">Seconds to wait, from a Retry-After header (typically on 429).</param>
+/// <param name="Raw">Every rate-limit-related header, verbatim, for inspection.</param>
+public sealed record CsFloatRateLimit(
+    int? Limit,
+    int? Remaining,
+    string? Reset,
+    int? RetryAfter,
+    IReadOnlyDictionary<string, string> Raw)
+{
+    public static readonly CsFloatRateLimit None =
+        new(null, null, null, null, new Dictionary<string, string>());
+
+    /// <summary>True when the API reports zero requests remaining.</summary>
+    public bool IsExhausted => Remaining is <= 0;
+
+    public override string ToString() =>
+        Raw.Count == 0
+            ? "rate-limit: (no headers)"
+            : "rate-limit: " + string.Join(", ", Raw.Select(kv => $"{kv.Key}={kv.Value}"));
+}