feat: #152 viewer XLSX — affichage multi-feuilles, édition des cellules et téléchargement des .xlsx

- backend/xlsx_reader.py : rend openpyxl en tableaux HTML (plafond 500x40 par feuille)
- PUT /api/file/{vault}/xlsx/save : service edit_xlsx_cells (backup avant écriture, refs A1 validées)
- frontend : renderXlsxViewer (onglets, contenteditable, sauvegarde par feuille)
- docs : CHANGELOG [Unreleased], Roadmap index #152, archive, README FR/EN, exemple OpenAPI

backend/xlsx_reader.py

@@ -0,0 +1,86 @@
+"""Render ``.xlsx`` workbooks as HTML tables for the viewer (#xlsx).
+
+Read-only: formulas are shown as their text (``data_only=False``) so a
+round-trip through the viewer never depends on Excel's cached values.
+Write-side lives in ``backend.services.mutations.edit_xlsx_cells``.
+"""
+
+from __future__ import annotations
+
+import html
+from datetime import date, datetime
+from pathlib import Path
+from typing import Any
+
+from openpyxl import load_workbook
+from openpyxl.utils import get_column_letter
+
+# ponytail: hard caps bound the rendered grid (500 rows x 40 cols per sheet).
+# Raise them, or paginate per sheet, if a real workbook needs more.
+MAX_ROWS = 500
+MAX_COLS = 40
+
+
+def _fmt(value: Any) -> str:
+    if value is None:
+        return ""
+    if isinstance(value, datetime):
+        return value.strftime("%Y-%m-%d %H:%M")
+    if isinstance(value, date):
+        return value.isoformat()
+    return str(value)
+
+
+def _trim(grid: list[list[str]]) -> list[list[str]]:
+    """Drop trailing empty rows and columns (openpyxl pads to max_col)."""
+    while grid and not any(grid[-1]):
+        grid.pop()
+    if not grid:
+        return grid
+    width = 0
+    for row in grid:
+        for i in range(len(row) - 1, -1, -1):
+            if row[i]:
+                width = max(width, i + 1)
+                break
+    return [row[:width] for row in grid]
+
+
+def _table(grid: list[list[str]]) -> str:
+    if not grid:
+        return "<p><em>Feuille vide</em></p>"
+    n_cols = max(len(row) for row in grid)
+    out = [
+        (
+            '<div class="csv-table-wrapper"><table class="csv-table xlsx-table">'
+            '<thead><tr><th class="xlsx-corner"></th>'
+        )
+    ]
+    out += [f"<th>{get_column_letter(c)}</th>" for c in range(1, n_cols + 1)]
+    out.append("</tr></thead><tbody>")
+    for r, row in enumerate(grid, start=1):
+        out.append(f'<tr><th class="xlsx-rownum">{r}</th>')
+        for c, val in enumerate(row, start=1):
+            ref = f"{get_column_letter(c)}{r}"
+            out.append(f'<td data-cell="{ref}">{html.escape(val)}</td>')
+        out.append("</tr>")
+    out.append("</tbody></table></div>")
+    return "".join(out)
+
+
+def render_sheets(file_path: Path) -> list[dict[str, str]]:
+    """Return ``[{"name": sheet_title, "html": table_html}, ...]``."""
+    wb = load_workbook(str(file_path), read_only=True, data_only=False)
+    try:
+        sheets = []
+        for ws in wb.worksheets:
+            grid = [
+                [_fmt(v) for v in row]
+                for row in ws.iter_rows(
+                    min_row=1, max_row=MAX_ROWS, max_col=MAX_COLS, values_only=True
+                )
+            ]
+            sheets.append({"name": ws.title, "html": _table(_trim(grid))})
+        return sheets
+    finally:
+        wb.close()