feat(pdf): Dec/Jan-aware year inference + filename hint + override

Previous year inference picked ``period_end_iso[:4]`` for every
short date, which fails on statements that cross the Dec/Jan
boundary. A "12/30" row in a 2024-12-16 to 2025-01-15 statement
got 2025-12-30 (wrong) instead of 2024-12-30.

New cascade for ``_infer_year_for_short_date``:

1. **``override_year``** — caller supplies it (new ``"Override
   year for short dates"`` field in Scan options). Beats every
   heuristic. Empty by default; the page validates the value
   is a 4-digit-looking integer in 1900-2100 and falls back to
   automatic on garbage input.

2. **Statement period start + end** — the function now takes
   BOTH dates and generates candidates with every distinct year
   in the period (one year for same-year statements, two for
   Dec/Jan boundaries). The picker scores each candidate by
   distance from the period: candidates inside the period
   score 0, candidates outside score ``min(|days from start|,
   |days from end|)``. Lowest-distance candidate wins. So:

     - ``12/30`` + period 2024-12-16 to 2025-01-15 → 2024-12-30
       (inside period, score 0)
     - ``01/05`` + same period → 2025-01-05 (inside, score 0)
     - ``12/15`` + same period → 2024-12-15 (1 day before,
       closer than 2025-12-15 which is 11 months after)

3. **``filename_year_hint``** — fallback when the statement
   period regex misses the bank's specific layout. The page
   passes ``year_from_filename(upload.name)`` automatically so
   files like ``eStmt_2025-01-13.pdf`` get year 2025 even if
   the PDF's text doesn't yield a parseable period. The regex
   matches the first ``20XX`` token bounded by non-digits.

Both new helpers (``year_from_filename`` and the new
``_try_short_date_with_year`` factor-out) are exported and
tested. 16 new tests cover: within-period inference (same-year
sanity), Dec/Jan boundary cases for both sides, the
just-before-period closer-distance case, override priority,
filename fallback, no-signal None, dash-format / month-name
shorthand round-trip, garbage input, filename year extraction
(eStmt pattern, embedded, first-match-wins, no-match, empty).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/gui/pages/10_PDF_Extractor.py

@@ -32,6 +32,7 @@ from src.pdf_extract import (
     format_amount,
     ocr_available,
     scan_pdf_for_transactions,
+    year_from_filename,
 )
 
 
@@ -179,6 +180,40 @@ with st.expander("Scan options", expanded=False):
             ),
         )
 
+    # Year override for short dates. Empty by default — the
+    # scanner uses statement-period detection + filename year hint
+    # automatically. Set this when the statement period regex
+    # misses on a particular bank's layout, or when you want to
+    # force a specific year (e.g., historical reconciliation).
+    year_override_str = st.text_input(
+        "Override year for short dates (optional)",
+        value="",
+        help=(
+            "Short dates like ``01/13`` get bound to a year by the "
+            "scanner — statement period first, then filename year, "
+            "then this override. Leave blank for automatic. Enter "
+            "a 4-digit year (e.g., 2025) to force every short date "
+            "to that year. Won't affect dates that already have a "
+            "year (``01/13/2025``)."
+        ),
+    )
+    try:
+        year_override = (
+            int(year_override_str) if year_override_str.strip() else None
+        )
+        if year_override is not None and not (1900 <= year_override <= 2100):
+            st.warning(
+                f"Year override {year_override} looks wrong — using "
+                "automatic detection instead."
+            )
+            year_override = None
+    except ValueError:
+        st.warning(
+            f"Year override {year_override_str!r} isn't a number — "
+            "using automatic detection instead."
+        )
+        year_override = None
+
 # Persistent stash + rotating widget key. See K_UPLOADS / K_UPLOAD_COUNTER
 # docstrings for why the counter exists.
 pdf_uploads: dict = st.session_state.setdefault(K_UPLOADS, {})
@@ -425,6 +460,8 @@ if scan_clicked and pdf_uploads:
                     negative_in_parens=negative_in_parens,
                     allow_ocr=use_ocr,
                     output_date_format=output_date_format,
+                    filename_year_hint=year_from_filename(name),
+                    year_override=year_override,
                 )
                 for r in rows:
                     r["source_file"] = name