feat: add Sign PDF tool (draw/type/upload signatures, place on a PDF) (#370)

Draw, type, or upload a signature and place resizable/rotatable copies across PDF pages; output flattened server-side with PyMuPDF. Visual electronic signature, not cryptographic. New interactive-sign display mode (pdf.js + Konva) and a custom docs-pool route.

packages/ai/python/dispatcher.py

@@ -97,6 +97,7 @@ DOCS_SCRIPTS = {
     "doc_to_word",
     "doc_metadata",
     "doc_html_pdf",
+    "doc_sign",
 }
 
 if DISPATCHER_PROFILE == "docs":

packages/ai/python/doc_sign.py

@@ -0,0 +1,57 @@
+"""Stamp signature images onto a PDF and save a flattened copy.
+Args: {"input": in, "output": out, "signatures": [paths], "placements": [
+  {"sig": idx, "page": 0-based, "x": 0..1, "y": 0..1, "w": 0..1, "h": 0..1}
+]}. Coordinates are page fractions, top-left origin. Each signature PNG is
+already rotated; insert_image is always axis-aligned. Prints {"ok": true,
+"placed": N}. insert_image draws into page content, so output is flattened."""
+import json
+import sys
+
+
+def main():
+    args = json.loads(sys.argv[1]) if len(sys.argv) > 1 else {}
+    path = args.get("input")
+    out = args.get("output")
+    signatures = args.get("signatures") or []
+    placements = args.get("placements") or []
+    if not path or not out or not isinstance(placements, list) or not placements:
+        print(json.dumps({"error": "missing input/output/placements"}))
+        sys.exit(1)
+    try:
+        import fitz
+    except ImportError:
+        print(json.dumps({"error": "PyMuPDF not installed"}))
+        sys.exit(1)
+    try:
+        doc = fitz.open(path)
+        page_count = doc.page_count
+        for p in placements:
+            page_no = p.get("page")
+            sig_idx = p.get("sig")
+            if not isinstance(page_no, int) or page_no < 0 or page_no >= page_count:
+                print(json.dumps({"error": f"page index {page_no} out of range (0..{page_count - 1})"}))
+                sys.exit(1)
+            if not isinstance(sig_idx, int) or sig_idx < 0 or sig_idx >= len(signatures):
+                print(json.dumps({"error": f"signature index {sig_idx} out of range"}))
+                sys.exit(1)
+            page = doc[page_no]
+            r = page.rect  # rotation-aware; x0/y0 carry the CropBox origin
+            x0, y0, w, h = r.x0, r.y0, r.width, r.height
+            fx, fy, fw, fh = (float(p["x"]), float(p["y"]), float(p["w"]), float(p["h"]))
+            rect = fitz.Rect(
+                x0 + fx * w, y0 + fy * h, x0 + (fx + fw) * w, y0 + (fy + fh) * h
+            )
+            with open(signatures[sig_idx], "rb") as f:
+                page.insert_image(rect, stream=f.read(), keep_proportion=False)
+        doc.save(out, garbage=4, deflate=True)
+        doc.close()
+        print(json.dumps({"ok": True, "placed": len(placements)}))
+    except SystemExit:
+        raise
+    except Exception as exc:  # noqa: BLE001
+        print(json.dumps({"error": str(exc)}))
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()