feat: API-Key Health-Check für Anthropic-Keys

- POST /api/admin/api-keys/{keyId}/check Endpoint
- Sendet minimale Anfrage an Anthropic API, liest Rate-Limit-Headers
- Plan-Erkennung: Max (Overage > 0), Pro (kein Fallback-Header), Pro/Max (sonst), API Console
- Budget-Auslastung: 5h + 7d + Overage mit Status-Warnings
- Frontend: Heartbeat-Button zeigt Ergebnis inline unter dem Key-Eintrag
- apiCheckApiKey() API-Funktion

Endpoints/ApiKeysEndpoint.cs

@@ -1,5 +1,8 @@
 using System;
 using System.Linq;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Text;
 using System.Text.Json;
 using System.Threading.Tasks;
 using Gott.Extensions;
@@ -20,6 +23,7 @@ public static class ApiKeysEndpoint
         app.MapPut("/api/admin/api-keys/{keyId}/activate", HandleActivate);
         app.MapPut("/api/admin/api-keys/{keyId}/deactivate", HandleDeactivate);
         app.MapDelete("/api/admin/api-keys/{keyId}", HandleDelete);
+        app.MapPost("/api/admin/api-keys/{keyId}/check", HandleCheck);
     }
 
     private static async Task HandleGetAll(HttpContext ctx, DatabaseService db)
@@ -170,5 +174,125 @@ public static class ApiKeysEndpoint
         await ctx.Response.WriteAsJsonAsync(new { ok = true });
     }
 
+    private static async Task HandleCheck(HttpContext ctx, IHttpClientFactory httpFactory, DatabaseService db, string keyId)
+    {
+        if (!ctx.IsAdmin()) { ctx.Response.StatusCode = 403; return; }
 
+        var existing = await db.GetApiKey(keyId);
+        if (existing == null)
+        {
+            ctx.Response.StatusCode = 404;
+            await ctx.Response.WriteAsJsonAsync(new { error = "Key nicht gefunden" });
+            return;
+        }
+
+        if (existing.Provider != "anthropic")
+        {
+            ctx.Response.StatusCode = 400;
+            await ctx.Response.WriteAsJsonAsync(new { error = "Check nur für Anthropic-Keys verfügbar" });
+            return;
+        }
+
+        try
+        {
+            var client = httpFactory.CreateClient();
+            client.Timeout = TimeSpan.FromSeconds(30);
+
+            var payload = JsonSerializer.Serialize(new
+            {
+                model = "claude-sonnet-4-20250514",
+                max_tokens = 1,
+                messages = new[] { new { role = "user", content = "hi" } }
+            });
+
+            var request = new HttpRequestMessage(HttpMethod.Post, "https://api.anthropic.com/v1/messages");
+            request.Headers.Add("x-api-key", existing.ApiKey);
+            request.Headers.Add("anthropic-version", "2023-06-01");
+            request.Content = new StringContent(payload, Encoding.UTF8, "application/json");
+
+            var resp = await client.SendAsync(request);
+            var headers = resp.Headers;
+
+            string GetHeader(string name)
+            {
+                if (headers.TryGetValues("anthropic-ratelimit-" + name, out var v1))
+                    return string.Join("", v1);
+                if (headers.TryGetValues(name, out var v2))
+                    return string.Join("", v2);
+                return null;
+            }
+
+            if (resp.StatusCode == System.Net.HttpStatusCode.Unauthorized)
+            {
+                await ctx.Response.WriteAsJsonAsync(new { status = "error", message = "Ungültig oder abgelaufen (401)" });
+                return;
+            }
+            if (resp.StatusCode == (System.Net.HttpStatusCode)429)
+            {
+                await ctx.Response.WriteAsJsonAsync(new { status = "error", message = "Rate Limited (429)" });
+                return;
+            }
+            if (resp.StatusCode == System.Net.HttpStatusCode.Forbidden)
+            {
+                await ctx.Response.WriteAsJsonAsync(new { status = "error", message = "Insufficient Quota (403)" });
+                return;
+            }
+            if ((int)resp.StatusCode >= 400)
+            {
+                await ctx.Response.WriteAsJsonAsync(new { status = "error", message = "API-Fehler (" + (int)resp.StatusCode + ")" });
+                return;
+            }
+
+            // Key ist gültig – Header auslesen
+            var d7Util = GetHeader("unified-7d-utilization");
+            var d5hUtil = GetHeader("unified-5h-utilization");
+            var overageUtil = GetHeader("unified-overage-utilization");
+            var d7Status = GetHeader("unified-7d-status");
+            var d5hStatus = GetHeader("unified-5h-status");
+            var overageStatus = GetHeader("unified-overage-status");
+
+            // Subscription-Keys haben unified-* Headers, API-Keys nicht
+            var isSubscription = d7Util != null || d5hUtil != null;
+            var fallbackPct = GetHeader("unified-fallback-percentage");
+
+            // Plan-Erkennung:
+            // - overage > 0 → definitiv MAX (Extra Usage aktiv, nur bei Max sinnvoll nutzbar)
+            // - kein fallback-percentage Header → PRO
+            // - sonst → Pro/Max (nicht unterscheidbar)
+            string keyType;
+            if (!isSubscription)
+                keyType = "API Console";
+            else if (overageUtil != null && double.TryParse(overageUtil, System.Globalization.NumberStyles.Float, System.Globalization.CultureInfo.InvariantCulture, out var ovCheck) && ovCheck > 0)
+                keyType = "Max";
+            else if (fallbackPct == null)
+                keyType = "Pro";
+            else
+                keyType = "Pro/Max";
+
+            double? usage7d = null, usage5h = null, overage = null;
+            if (d7Util != null && double.TryParse(d7Util, System.Globalization.NumberStyles.Float, System.Globalization.CultureInfo.InvariantCulture, out var d7))
+                usage7d = Math.Round(d7 * 100, 1);
+            if (d5hUtil != null && double.TryParse(d5hUtil, System.Globalization.NumberStyles.Float, System.Globalization.CultureInfo.InvariantCulture, out var d5))
+                usage5h = Math.Round(d5 * 100, 1);
+            if (overageUtil != null && double.TryParse(overageUtil, System.Globalization.NumberStyles.Float, System.Globalization.CultureInfo.InvariantCulture, out var ov))
+                overage = Math.Round(ov * 100, 1);
+
+            await ctx.Response.WriteAsJsonAsync(new
+            {
+                status = "ok",
+                keyType,
+                isSubscription,
+                usage7d,
+                usage5h,
+                overage,
+                status7d = d7Status,
+                status5h = d5hStatus,
+                statusOverage = overageStatus
+            });
+        }
+        catch (Exception ex)
+        {
+            await ctx.Response.WriteAsJsonAsync(new { status = "error", message = ex.Message });
+        }
+    }
 }