ingest: Use timestamp-based filenames for WhatsApp files

WhatsApp files arrive with empty or non-descriptive body fields. Rather
than falling back to generic names like "image.jpg" or "document.pdf",
generate names from the event timestamp:

  whatsapp_YYYY-MM-DD_HH-MM-SS.jpg
  whatsapp_YYYY-MM-DD_HH-MM-SS.pdf

If the body contains text (e.g. a caption), it is prepended:

  Test - whatsapp_2026-03-11_23-35-13.pdf

Files whose body already ends in the correct extension are used as-is.

ingest.py

@@ -214,16 +214,32 @@ def is_supported_file(event) -> bool:
     return False
 
 
+def _whatsapp_filename(ts_ms: int, is_pdf: bool, body: str) -> str:
+    """Generate a filename from the event timestamp, optionally prefixed with the body text."""
+    from datetime import datetime, timezone
+    dt = datetime.fromtimestamp(ts_ms / 1000, tz=timezone.utc)
+    stamp = dt.strftime("%Y-%m-%d_%H-%M-%S")
+    ext = ".pdf" if is_pdf else ".jpg"
+    base = f"whatsapp_{stamp}{ext}"
+    if body:
+        return f"{body} - {base}"
+    return base
+
+
 def extract_event_fields(event) -> tuple[str, str, str, Optional[str], bool]:
     """Returns (event_id, filename, mxc_url, encryption_info_json_or_None, is_pdf)."""
     if isinstance(event, BadEvent):
         content = event.source.get("content", {})
-        filename = content.get("body", "unknown")
+        body = content.get("body", "")
         file_info = content.get("file", {})
         is_pdf = content.get("msgtype") == "m.file"
+        ext = ".pdf" if is_pdf else ".jpg"
+        filename = body if body.lower().endswith(ext) else _whatsapp_filename(event.server_timestamp, is_pdf, body)
         return event.event_id, filename, file_info["url"], json.dumps(file_info), is_pdf
     is_pdf = isinstance(event, RoomMessageFile)
-    filename = event.body or ("document.pdf" if is_pdf else "image.jpg")
+    ext = ".pdf" if is_pdf else ".jpg"
+    body = event.body or ""
+    filename = body if body.lower().endswith(ext) else _whatsapp_filename(event.server_timestamp, is_pdf, body)
     return event.event_id, filename, event.url, None, is_pdf
 
 
@@ -500,7 +516,7 @@ async def retry_loop(
 
         for event_id, filename, mxc_url, enc_info in rows:
             log.info("Retrying %s (%s)", filename, event_id)
-            is_pdf = (filename or "").lower().endswith(".pdf")
+            is_pdf = filename.lower().endswith(".pdf")
             await process_event(event_id, filename, mxc_url, enc_info, is_pdf,
                                 matrix_client, db, paperless)