feat: deliver in chosen format (not forced JPEG); wire output_ext through jobs/Telegram/MCP

- delivery.ts: upload the stored result in its chosen format (output_ext,
  global or per-recipe) instead of always converting non-alpha to JPEG.
- jobs POST froze the snapshot without output_ext -> per-conversion/per-recipe
  format choice was silently dropped. Now carried through.
- telegram.ts: recipe snapshots carry output_ext + delivery_target_id
  (custom formats already flow via output_format).
- mcp/klarbild-mcp.mjs: process_images gains tasks, output_ext, orientation,
  crop_mode, contour_mm, picdrop_gallery; job_status shows finished_at + errors.
- Docs: llms.txt, mcp/README, changelog updated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNQ8ghPfzAfsyVYd6HgFb6

src/pages/api/jobs/index.ts

@@ -57,6 +57,7 @@ export const POST: APIRoute = async ({ request, locals }) => {
     delivery: snapshot.delivery || 'library',
     picdrop_gallery: snapshot.picdrop_gallery ?? null,
     delivery_target_id: snapshot.delivery_target_id ?? null,
+    output_ext: (snapshot.output_ext === 'jpg' || snapshot.output_ext === 'png') ? snapshot.output_ext : null,
   };
 
   // Private Session: nur wenn global erlaubt oder für den Nutzer erzwungen.