Equity PAPER + Alpaca native paper should route to paper-api (not local pt_orders)

Summary

On Equity with UI trading mode = PAPER and a broker that has native paper (Alpaca PK keys → paper-api.alpaca.markets), Fincept currently routes orders through the local paper engine (pt_place_order / pt_orders / OrderMatcher) instead of the broker adapter. The result is that a "paper" ticket never hits Alpaca's paper REST API, so the blotter and the broker disagree.

Expected

When BrokerProfile.has_native_paper == true and the account is in PAPER mode, place / cancel / cancel-all / blotter should use the broker adapter (Alpaca → https://paper-api.alpaca.markets), while keeping the UI mode tag as paper. Local pt_* simulation should remain only for brokers without native paper.

Actual

• Equity PAPER → UnifiedTrading::place_paper_order_for_account → pt_place_order only
• has_native_paper is set on Alpaca (and others) but ignored for placement
• Live REST path (AlpacaBroker::place_order + trading_url) is only used when UI mode is live

Proposed fix (minimal, one logical change)

1. UnifiedTrading::place_paper_order_for_account: if has_native_paper → place_live_order_for_account, stamp response mode = "paper"
2. Equity on_order_submitted / cancel: thin native-paper path through UnifiedTrading
3. Blotter / Streams: for native-paper, use broker get_orders (and related) instead of pt_get_orders*
4. AlpacaBroker::trading_url / place_order: hard guard — PK / additional_data=paper never use api.alpaca.markets

Proof (paper only)

After building with the patch on Windows:

• Fincept EQUITY · Alpaca focused · UI PAPER
• BUY 1 SPY LMT well below market
• Order appeared on Alpaca paper REST (GET /v2/orders) with Fincept client_order_id prefix fin…
• No new local pt_orders row for that submit
• Canceled via paper-api

Happy to open a topic-branch PR once this issue has scope:approved / help-wanted / good-first-issue per .github/CONTRIBUTING.md.

Platform

Windows (MSVC + Qt 6.8.3), Fincept Terminal 4.5.0 tree.