feat: append png after text notifications

feat: append png after summary notifications

feat: append png after direct text notifications

feat: add append-image notify config

docs: add append-image notify implementation plan

Merge remote-tracking branch 'origin/main'

docs: add append-image notify design spec

feat: prefer THS stock names before fallback

feat: prefer THS market metrics before fallback

feat: backfill THS realtime market metrics

fix: map THS free-float market value

feat: enrich THS market data with official endpoints

feat: wire TongHuaShun professional mode through pipeline

feat: prefer TongHuaShun market data when available

feat: add capability-aware TongHuaShun service methods