feat(market-data): add Router tick continuity

[LimiNode]

Summary

• connect TickSubscriptionRequest continuity to Router history-first delivery
• add tick prefill, gap detection, bounded recovery, retry, reconnect STALE/READY handling, sticky DEGRADED and exact-overlap deduplication
• keep event-oriented tick recovery inclusive: expected_interval_ms is only a suspicion threshold, the triggering tick is retained, and bounded chunks overlap without inventing tick slots
• use Intrade observed /price_now history through fetch_tick_history(); preserve distinct same-second observations
• align Intrade history requests to the provider clock/grid; estimate broker offset from a bounded median of recent time_ms - received_ms samples
• stop history recovery at the last completed Intrade provider boundary instead of rounding an off-grid live timestamp into the future
• document the EN/RU contract and register the regression suite

This PR is stacked on #164 (feat/intrade-observed-tick-history).

Verification

• Ubuntu Smoke run 34214674466: passed
• Windows Smoke run 34214674525: passed
• market_data_tick_continuity_test: 13/13 locally
• market_data_subscription_contract_test: 25/25
• market_data_router_test: 23/23
• market_data_continuity_test: 46/46
• market_data_tick_history_contract_test: 8/8
• intrade_observed_tick_history_test: passed in Ubuntu and Windows CI
• git diff --check: passed