fix(export): v4.7.3 tableaux + emojis en PDF/HTML

- Tableaux GFM rendus comme texte brut dans les exports HTML/PDF. Ajout d'un
  parseur de tableaux pipe (bloc 'table') + rendu <table> (thead/tbody,
  alignement gauche/centre/droite, bordures .ftable) dans blocks_to_html;
  blocks_to_markdown reconstruit un tableau pipe valide.
- Emojis 'carrés noirs' en PDF: xhtml2pdf n'embarque que des polices de base
  sans glyphes emoji. Moteur PDF -> WeasyPrint (tables CSS + emojis couleur via
  pango + fonts-noto-color-emoji installes dans l'image). Repli automatique sur
  xhtml2pdf quand weasyprint n'a pas ses libs natives (dev Windows).
- Dockerfile: libs weasyprint (pango/harfbuzz/gdk-pixbuf/shared-mime-info) +
  fonts-dejavu-core + fonts-noto-color-emoji. requirements: + weasyprint==69.0.
- Verifie en reel sur README.md: HTML = <table class=ftable> (thead/th, center);
  PDF 10 pages, texte de table present, Noto-Color-Emoji embarque + pixels
  colores confirmes. 199/199 tests (4 nouveaux).

app/services/export.py

@@ -171,6 +171,145 @@ def _page_source(page: dict):
     return "blocks", []
 
 
+# ── GFM pipe-table parsing (raw markdown → "table" block) ──
+
+_SEP_CELL = re.compile(r"^:?-+:?$")
+
+
+def _split_pipe_cells(line: str) -> list[str]:
+    """Split a GFM pipe row into trimmed cell strings."""
+    s = line.strip()
+    if s.startswith("|"):
+        s = s[1:]
+    if s.endswith("|") and not s.endswith(r"\|"):
+        s = s[:-1]
+    # split on unescaped pipes
+    cells: list[str] = []
+    cur: list[str] = []
+    i = 0
+    while i < len(s):
+        ch = s[i]
+        if ch == "\\" and i + 1 < len(s) and s[i + 1] == "|":
+            cur.append("|")
+            i += 2
+            continue
+        if ch == "|":
+            cells.append("".join(cur).strip())
+            cur = []
+            i += 1
+            continue
+        cur.append(ch)
+        i += 1
+    cells.append("".join(cur).strip())
+    return cells
+
+
+def _is_table_delimiter(line: str) -> bool:
+    s = line.strip()
+    if not s:
+        return False
+    if s.startswith("|"):
+        s = s[1:]
+    if s.endswith("|"):
+        s = s[:-1]
+    cells = [c.strip() for c in s.split("|")]
+    return bool(cells) and all(_SEP_CELL.match(c) for c in cells)
+
+
+def _parse_table_at(lines: list[str], i: int, n: int):
+    """If a GFM table starts at index i (header row + delimiter row), return
+    (table_block, next_index). Otherwise return None."""
+    header_cells = _split_pipe_cells(lines[i])
+    if len(header_cells) <= 1:
+        return None
+    if i + 1 >= n or not _is_table_delimiter(lines[i + 1]):
+        return None
+    sep_cells = _split_pipe_cells(lines[i + 1])
+    align = []
+    for c in sep_cells[: len(header_cells)]:
+        c = c.strip()
+        if c.startswith(":") and c.endswith(":"):
+            align.append("center")
+        elif c.endswith(":"):
+            align.append("right")
+        else:
+            align.append("left")
+    rows = [header_cells]
+    j = i + 2
+    while j < n:
+        s = lines[j].strip()
+        if not s or not s.startswith("|"):
+            break
+        cells = _split_pipe_cells(lines[j])
+        rows.append(cells)
+        j += 1
+    width = max(len(r) for r in rows)
+    pad = lambda r: r + [""] * (width - len(r))
+    align = (align + ["left"] * width)[:width]
+    return (
+        {
+            "type": "table",
+            "has_header": True,
+            "align": align,
+            "rows": [pad(r) for r in rows],
+        },
+        j,
+    )
+
+
+def _table_to_markdown(b: dict) -> str:
+    rows = b.get("rows") or []
+    if not rows:
+        return ""
+    align = b.get("align") or []
+    width = max(len(r) for r in rows)
+    align = (align + ["left"] * width)[:width]
+    out: list[str] = []
+
+    def rowline(r):
+        cells = list(r) + [""] * (width - len(r))
+        return "| " + " | ".join(cells) + " |"
+
+    for ri, r in enumerate(rows):
+        out.append(rowline(r))
+        if b.get("has_header") and ri == 0:
+            seps = []
+            for a in align:
+                if a == "center":
+                    seps.append(":---:")
+                elif a == "right":
+                    seps.append("---:")
+                else:
+                    seps.append(":---")
+            out.append("| " + " | ".join(seps) + " |")
+    return "\n".join(out)
+
+
+def _table_to_html(b: dict) -> str:
+    rows = b.get("rows") or []
+    if not rows:
+        return ""
+    align = b.get("align") or []
+    width = max(len(r) for r in rows)
+    align = (align + ["left"] * width)[:width]
+
+    def cell_html(tag, text, a):
+        style = f' style="text-align:{a};"' if a and a != "left" else ""
+        return f"<{tag}{style}>{_text(text)}</{tag}>"
+
+    def row_html(r, tag_default):
+        cells = list(r) + [""] * (width - len(r))
+        return "<tr>" + "".join(cell_html(tag_default, c, align[ci]) for ci, c in enumerate(cells)) + "</tr>"
+
+    header_rows = 1 if b.get("has_header") else 0
+    head = ""
+    if header_rows:
+        head = "<thead>" + "".join(row_html(r, "th") for r in rows[:header_rows]) + "</thead>"
+    tbody_rows = rows[header_rows:]
+    body = "<tbody>" + "".join(row_html(r, "td") for r in tbody_rows) + "</tbody>"
+    return f'<table class="ftable">{head}{body}</table>'
+
+
 # ── Markdown renderer (raw markdown → exportable fragments) ──
 
 def _md_to_blocks(md: str) -> list:
@@ -213,6 +352,14 @@ def _md_to_blocks(md: str) -> list:
                 i += 1  # closing fence
             blocks.append({"type": "code", "content": "\n".join(code), "language": lang})
             continue
+        if stripped.startswith("|"):
+            # GFM pipe table: header row immediately followed by a delimiter row
+            parsed = _parse_table_at(lines, i, n)
+            if parsed is not None:
+                flush_para()
+                tbl, i = parsed
+                blocks.append(tbl)
+                continue
         m = re.match(r"^(#{1,6})\s+(.*)$", stripped)
         if m and line == stripped:  # ATX heading must be whole line
             level = len(m.group(1))
@@ -344,6 +491,8 @@ def blocks_to_markdown(blocks: list) -> str:
             src = b.get("src") or ""
             alt = (b.get("alt") or "").strip() or "image"
             out.append(f"![{alt}]({src})")
+        elif t == "table":
+            out.append(_table_to_markdown(b))
         else:
             out.append(c)
     return "\n\n".join(filter(None, out))
@@ -444,6 +593,8 @@ def blocks_to_html(blocks: list) -> str:
             src = b.get("src") or ""
             alt = _text(b.get("alt"))
             parts.append(f'<figure><img src="{src}" alt="{alt}"><figcaption>{alt}</figcaption></figure>')
+        elif t == "table":
+            parts.append(_table_to_html(b))
         else:
             parts.append(f"<p>{c}</p>")
     return "\n".join(parts)
@@ -485,6 +636,10 @@ details[open] summary{margin-bottom:8px;}
 figure{margin:16px 0;text-align:center;}
 figure img{max-width:100%;border-radius:8px;}
 figcaption{font-size:13px;color:#8b949e;margin-top:6px;}
+.ftable{width:100%;border-collapse:collapse;margin:16px 0;font-size:14.5px;line-height:1.45;}
+.ftable th,.ftable td{border:1px solid #d8dee4;padding:7px 12px;vertical-align:top;}
+.ftable th{background:#f6f8fa;font-weight:600;}
+.ftable tr:nth-child(even) td{background:#fcfcfd;}
 .footer{margin-top:56px;padding-top:16px;border-top:1px solid #eaeef2;color:#8b949e;font-size:12px;display:flex;justify-content:space-between;}
 a{color:#0969da;}
 @media print{body{background:#fff;}.wrap{padding:0;max-width:100%;}}
@@ -548,6 +703,9 @@ pre{{background:#f4f4f4;padding:10px;font-size:10px;white-space:pre-wrap;}}
 code{{font-family:monospace;font-size:10px;}}
 blockquote{{border-left:3px solid #ccc;margin:8px 0;padding:2px 12px;font-style:italic;}}
 table{{border-collapse:collapse;width:100%;}}
+.ftable{{border-collapse:collapse;width:100%;margin:10px 0;}}
+.ftable th,.ftable td{{border:1px solid #999;padding:5px 8px;}}
+.ftable th{{background:#f0f0f0;font-weight:bold;}}
 hr{{border:none;border-top:1px solid #ddd;margin:16px 0;}}
 .todo{{margin:4px 0;}}
 .math{{font-style:italic;margin:10px 0;}}
@@ -561,8 +719,25 @@ hr{{border:none;border-top:1px solid #ddd;margin:16px 0;}}
 
 
 def page_to_pdf_bytes(page: dict) -> bytes:
-    """Render a page to a PDF (via xhtml2pdf)."""
+    """Render a page to a PDF.
+
+    Primary engine: WeasyPrint — renders colour emoji and proper CSS tables
+    (needs system libs: pango + fonts; available in the Docker image).
+    Fallback: xhtml2pdf (pure Python) when WeasyPrint's native libraries are
+    absent (e.g. a Windows dev host) — text/table content still exports,
+    though emoji are limited to monochrome by the engine.
+    """
+    # 1) WeasyPrint (best fidelity: colour emoji, CSS tables)
+    try:
+        from weasyprint import HTML
+
+        html = page_to_standalone_html(page, include_children=False)
+        return HTML(string=html, base_url=_data_root().as_uri() + "/").write_pdf()
+    except Exception:  # ImportError or missing native libs (OSError) -> fallback
+        pass
+    # 2) xhtml2pdf fallback (pure Python)
     from xhtml2pdf import pisa
+
     src = _pdf_html(page)
     buf = io.BytesIO()
     pdf = pisa.CreatePDF(src, dest=buf, encoding="utf-8")