Fix clipped receipt margins, add time-of-day naming, speed up rotation detection

- vision/document.py: pad_quad() expands the detected quad outward
  before warping so a straight-line contour fit doesn't clip the first
  character of every line on a slightly curled/wrinkled receipt
- ocr/extract.py + llm/vision.py: extract transaction time (HH:MM) so
  same-day repeat visits to a vendor get distinct filenames
  (2023-03-20_1525_walmart.pdf vs. a later same-day trip)
- vision/orient.py: downscale before Tesseract OSD/confidence-sweep
  rotation detection — this was the dominant cost in the detection
  phase (7x speedup: 472s -> 67s on a 36s test video)

paperpod/config.py

@@ -52,6 +52,9 @@ class DocumentConfig:
     # Fixes the "placed the document upside down" case, which otherwise
     # produces a fine-looking crop that OCR reads as garbage.
     auto_rotate: bool = True
+    # Expand the detected quad outward by this fraction before warping, to
+    # recover paper margins clipped by curl/wrinkles (see pad_quad).
+    pad_margin: float = 0.04
     # Tighten each crop to the actual paper region (removes mat margins and
     # hands hanging off the side of receipts) and inpaint fingers pressing
     # on the page. Content *under* a finger can't be recovered — it's filled