Get a trader's position timeline (unified identity resolver)

Unified trader-timeline route (#4975). {trader} accepts all four identity shapes - 0x... wallet, username, trd_-prefixed trader id, and bare integer id - resolved by the single shared trader-identity resolver. Returns stored Polymarket fills for one tracked trader in one market, newest first, with server-computed running_amount and running_avg_price. Only HOT and WARM tier traders are tracked; other traders return 404. Response payload matches the singular GET /api/v1/trader/{address}/position-timeline route for the same (trader, market), except for the per-request meta.request_id. The prior integer-id-only variant is preserved: the same path now accepts every identity shape.