Dashboard-Performance: API-Endpoints konsolidieren

Backend:
- GET /api/sessions: Git-Status inline integriert (parallel pro Session)
  - Neue Hilfsmethoden GetGitStatusSummaryAsync (Counts) und
    GetGitStatusDetailedAsync (Dateinamen, für Einzel-Endpoint)
  - GetSessionsWithStats gibt typisierte SessionWithStats zurück
  - Neue Models: SessionWithStats, GitStatusSummary
- GET /api/agents: Skills inline pro Agent integriert
  - SkillService als Parameter in HandleList
  - Skills als Array mit slug/name/description

Frontend:
- Dashboard: 1 paralleler Promise.all statt sequentieller Requests
  - Vorher: agents → sessions → N×git-status → M×agent-skills → cronjobs → shares
  - Nachher: Promise.all([agents, sessions, cronjobs, shares]) (4 Requests)
  - Git-Status direkt aus Session-Response, Skills aus Agent-Response
- Session-Page: Agent-Skills aus inline-Daten statt N×apiGetAgentSkills

Reduziert Dashboard-Requests von ~4+N+M auf 4 (fix).

Endpoints/AgentEndpoint.cs

@@ -1,3 +1,5 @@
+using System.Collections.Generic;
+using System.Linq;
 using System.Text.Json;
 using System.Threading.Tasks;
 using Gott.Extensions;
@@ -20,11 +22,51 @@ public static class AgentEndpoint
         app.MapDelete("/api/agents/{agentId}", HandleDelete);
     }
 
-    private static async Task HandleList(HttpContext ctx, DatabaseService db)
+    private static async Task HandleList(HttpContext ctx, DatabaseService db, SkillService skillService)
     {
         var userId = ctx.GetUserId();
         var agents = await db.GetAgents(userId);
-        await ctx.Response.WriteAsJsonAsync(agents);
+        var allSkills = skillService.GetAllSkills();
+        var skillMap = allSkills.ToDictionary(s => s.Slug);
+
+        var results = new List<object>();
+        foreach (var a in agents)
+        {
+            var agentSkillSlugs = await db.GetAgentSkills(a.AgentId);
+            var skills = agentSkillSlugs
+                .Where(slug => skillMap.ContainsKey(slug))
+                .Select(slug => new { slug, name = skillMap[slug].Name, description = skillMap[slug].Description })
+                .ToList();
+
+            results.Add(new
+            {
+                a.AgentId,
+                a.Name,
+                a.Avatar,
+                a.Description,
+                a.Model,
+                a.ToolChoice,
+                a.CustomCommands,
+                a.AutoCommit,
+                a.UseSoul,
+                a.UseIdentity,
+                a.UseUserInfo,
+                a.UseMemory,
+                a.UseWebSearch,
+                a.WebSearchVersion,
+                a.AllowUserChoice,
+                a.TaskInstruction,
+                a.AvatarScale,
+                a.AvatarOffsetX,
+                a.AvatarOffsetY,
+                a.IsDeleted,
+                a.CreatedAt,
+                a.UpdatedAt,
+                Skills = skills
+            });
+        }
+
+        await ctx.Response.WriteAsJsonAsync(results);
     }
 
     private static async Task HandleGet(HttpContext ctx, DatabaseService db)