feat: add RFQ trade history support

[harley-poly]

Changes

Add rfqs.trades() to both Python clients for authenticated RFQ trade history, with typed filters, responses and the existing live rfqTrade event. Preserve decimal strings, timestamps and opaque cursors through the existing transport.

Document manual pagination, empty continuation pages and recovery from the live stream using overlapping queries and trade-ID deduplication. These are anonymous original fills; later corrections and busts are not reflected.

Follows https://github.com/Polymarket/go-gateway-us/pull/2307. Sets version 2.3.0. This is independent of #14 and will release first; the batch-order follow-up will use 2.4.0.

Testing

• 223 tests pass on Python 3.13/websockets 17.2 and Python 3.10/websockets 13.0.
• 17 new tests cover signed requests, filters/cursors, exact response values, empty-page continuation, authentication/API errors and live payloads over a local WebSocket.
• Typed consumers cover both clients and nullable trade/timestamp fields. Ruff lint/format, mypy and wheel/sdist build pass.
• No live API or trading calls.

Checklist

• Tests pass (pytest)
• Linting passes (ruff check .)
• Types check (mypy polymarket_us)

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Note

Low Risk
Additive SDK surface (new resource method and types) with tests; no changes to order placement or core auth transport beyond a new authenticated GET.

Overview
Adds authenticated RFQ trade history via client.rfqs.trades() on sync and async clients, calling GET /v1/rfqs/trades with typed GetRFQTradesParams / GetRFQTradesResponse and RFQTrade records (decimal strings, cursor pagination).

Extends private rfq_event typings with rfqTrade so live anonymous RFQ fills match the history shape. README documents manual pagination, empty pages with nonempty cursors, eventual consistency, and gap recovery via overlapping queries and tradeId deduplication.

Bumps package version to 2.3.0 and adds HTTP/WebSocket regression tests for signing, filters, auth/errors, and live rfqTrade callbacks.

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