Add image preview support: Krea-tag parsing with modal, file-explorer preview, skill output endpoint, increase execute timeout to 180s

- SkillEndpoint: GET /api/skills/{slug}/output/{filename} for skill output files
- WorkspaceEndpoint: GET /api/workspace/raw for raw file serving (images)
- File-Explorer: Image preview for png/jpg/gif/webp/svg/bmp/ico
- Chat UI: Parse [Krea: filename] tags into clickable chips with image modal
- ToolService: Increase execute timeout from 30s to 180s for long-running skills

Endpoints/SkillEndpoint.cs

@@ -1,3 +1,6 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Text.Json;
 using System.Threading.Tasks;
@@ -10,11 +13,24 @@ namespace Gott.Endpoints;
 
 public static class SkillEndpoint
 {
+    private static readonly Dictionary<string, string> MimeTypes = new(StringComparer.OrdinalIgnoreCase)
+    {
+        { ".png", "image/png" }, { ".jpg", "image/jpeg" }, { ".jpeg", "image/jpeg" },
+        { ".gif", "image/gif" }, { ".webp", "image/webp" }, { ".svg", "image/svg+xml" },
+        { ".bmp", "image/bmp" }, { ".ico", "image/x-icon" },
+        { ".pdf", "application/pdf" },
+        { ".mp4", "video/mp4" }, { ".webm", "video/webm" },
+        { ".mp3", "audio/mpeg" }, { ".wav", "audio/wav" }, { ".ogg", "audio/ogg" },
+    };
+
     public static void MapSkillEndpoints(this IEndpointRouteBuilder app)
     {
         // Skills (Dateisystem-basiert)
         app.MapGet("/api/skills", HandleListSkills);
 
+        // Skill-Output-Dateien (Bilder etc.)
+        app.MapGet("/api/skills/{slug}/output/{filename}", HandleSkillOutput);
+
         // Agent ↔ Skill Zuordnung
         app.MapGet("/api/agents/{agentId}/skills", HandleGetAgentSkills);
         app.MapPut("/api/agents/{agentId}/skills", HandleSetAgentSkills);
@@ -79,4 +95,44 @@ public static class SkillEndpoint
         await db.RemoveAgentSkill(agentId, slug);
         ctx.Response.StatusCode = 204;
     }
+
+    private static async Task HandleSkillOutput(HttpContext ctx, SkillService skillService)
+    {
+        var slug = ctx.Request.RouteValues["slug"]?.ToString();
+        var filename = ctx.Request.RouteValues["filename"]?.ToString();
+
+        if (string.IsNullOrEmpty(slug) || string.IsNullOrEmpty(filename))
+        {
+            ctx.Response.StatusCode = 400;
+            return;
+        }
+
+        // Sicherheit: Keine Pfad-Traversals erlauben
+        if (filename.Contains("..") || filename.Contains('/') || filename.Contains('\\'))
+        {
+            ctx.Response.StatusCode = 400;
+            return;
+        }
+
+        var skill = skillService.GetSkill(slug);
+        if (skill == null)
+        {
+            ctx.Response.StatusCode = 404;
+            return;
+        }
+
+        var filePath = Path.Combine(skill.Path, "output", filename);
+        if (!File.Exists(filePath))
+        {
+            ctx.Response.StatusCode = 404;
+            return;
+        }
+
+        var ext = Path.GetExtension(filename);
+        var contentType = MimeTypes.GetValueOrDefault(ext, "application/octet-stream");
+
+        ctx.Response.ContentType = contentType;
+        ctx.Response.Headers["Cache-Control"] = "private, max-age=3600";
+        await ctx.Response.SendFileAsync(filePath);
+    }
 }