bug: preserve TPEx market in Yahoo OHLCV fallback

[cct08311github]

Summary

Recent commit 6608f5cd5e4d8840ee80f7bdfd20236df262c0e6 added Yahoo Finance OHLCV fallback in run_daily_fetch(), but the new path assumes every symbol in eod_prices is TWSE. The schema explicitly supports both TWSE and TPEx.

Evidence

• src/openclaw/market_data_fetcher.py wrote Yahoo fallback rows with a hardcoded market='TWSE'.
• src/openclaw/agents/eod_analysis.py and src/openclaw/eod_ingest.py pass SELECT DISTINCT symbol FROM eod_prices, which includes TPEx holdings.
• This causes TPEx symbols to go through the wrong fallback path and be persisted back with the wrong market.

Minimal fix

• Look up each symbol's market from existing eod_prices rows.
• Skip TWSE STOCK_DAY for TPEx symbols.
• Use Yahoo .TWO for TPEx symbols and preserve the original market on insert.

Verification

• Add a regression test in src/tests/test_market_data_fetcher.py covering a TPEx symbol through Yahoo fallback.
• Run pytest -q src/tests/test_market_data_fetcher.py.

[cct08311github]

Opened PR #482 to fix the TPEx Yahoo OHLCV fallback market regression: #482