[verified] Add Siamchart SET50 fundamental scraper (financial table + stock-info ratios/income)

- fetch_financial(group): parse Siamchart JS store_real_data array -> EPS/Rev/NP (5yr) + PE for every symbol
- parse_stock_info_html: head1/body key ratios (PE/P/BV/D/E/DPS/EPS/ROAA/ROAE/NPM/Yield) + income statement (QoQ/YoY)
- collect_siamchart.py CLI: --group/--stock-info/--with-info, timestamped JSON snapshot
- build_url validates group against ^[A-Z0-9]+(?:-[A-Z0-9]+)*$ (blocker closed)
- 10 unit tests; full backend suite 135 OK; independent review deleg_ad2b8dc7 passed=true

[verified] tags from requesting-code-review pipeline.

backend/scripts/collect_siamchart.py

@@ -0,0 +1,92 @@
+"""Collect Siamchart SET50 fundamental data into a local timestamped snapshot.
+
+Two modes:
+
+  --group SET50           parse the whole-group financial table (EPS/Rev/NP/PE
+                          for every symbol in the group) into `rows`.
+  --stock-info SYMBOL     parse one symbol's key ratios + income statement into
+                          `info`.
+
+With --with-info, after fetching the group table we also fetch each symbol's
+stock-info page (ratios + income) and attach them under `details[SYMBOL]`. This
+is the full "所有 in one" fundamental snapshot. The output is written to the
+`--out` path with a UTC timestamp and a data/parser provenance header.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+from datetime import datetime, timezone
+from pathlib import Path
+
+from app import siamchart
+
+
+def _now_utc() -> str:
+    return datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--group", default=None,
+                        help="Siamchart financial group (e.g. SET50).")
+    parser.add_argument("--stock-info", dest="stock_info", metavar="SYMBOL", default=None,
+                        help="Fetch one symbol's stock-info instead of a group table.")
+    parser.add_argument("--with-info", action="store_true",
+                        help="After the group table, also fetch each symbol's stock-info.")
+    parser.add_argument("--out", type=Path, default=None,
+                        help="Write the JSON snapshot to this file (default: stdout).")
+    parser.add_argument("--timeout", type=float, default=30.0)
+    args = parser.parse_args()
+
+    if args.stock_info and args.group:
+        parser.error("choose either --group or --stock-info, not both")
+    if not args.stock_info and not args.group:
+        parser.error("provide --group or --stock-info")
+
+    payload: dict = {
+        "source": "siamchart",
+        "retrieved_at": _now_utc(),
+    }
+
+    if args.stock_info:
+        info = siamchart.fetch_stock_info(args.stock_info, timeout=args.timeout)
+        payload.update({
+            "mode": "stock-info",
+            "symbol": info.symbol,
+            "url": siamchart._build_stock_info_url(info.symbol),
+            "info": info.to_dict(),
+        })
+    else:
+        rows = siamchart.fetch_financial(args.group, timeout=args.timeout)
+        payload.update({
+            "mode": "group",
+            "group": args.group,
+            "url": siamchart.build_url(args.group),
+            "count": len(rows),
+            "rows": [row.to_dict() for row in rows],
+        })
+        if args.with_info:
+            details = {}
+            for row in rows:
+                try:
+                    info = siamchart.fetch_stock_info(row.symbol, timeout=args.timeout)
+                    details[row.symbol] = info.to_dict()
+                except siamchart.SiamchartError as exc:
+                    details[row.symbol] = {"error": str(exc)}
+            payload["details"] = details
+            payload["details_count"] = len(details)
+
+    text = json.dumps(payload, ensure_ascii=False, sort_keys=True, indent=2)
+    if args.out:
+        args.out.parent.mkdir(parents=True, exist_ok=True)
+        args.out.write_text(text, encoding="utf-8")
+        print(f"wrote {payload.get('count', payload.get('symbol', ''))} -> {args.out}")
+    else:
+        print(text)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())