Add deformed to negative prompt

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/negative_prompt.txt

@@ -1 +1 @@
-worst quality, low quality, bad anatomy, bad hands, text, error, missing fingers, extra digit, fewer digits, cropped, jpeg artifacts, signature, watermark, username, blurry
+worst quality, low quality, bad anatomy, bad hands, text, error, missing fingers, extra digit, fewer digits, cropped, jpeg artifacts, signature, watermark, username, blurry, deformed