Pipeline API — Phase 3: Live trading

[MDUYN]

Part of #438. Depends on Phase 1 (#501) and Phase 2 (#502).

Scope

Add Pipeline support to live trading, with the explicit caveat that v1 supports only daily timeframes and small universes.

Deliverables

• Batched / async OHLCV fetch in CCXTOHLCVDataProvider. CCXT's fetch_ohlcv is per-symbol; need rate-limit-aware concurrent fan-out.
• Universe-refresh hook on Pipeline: refresh_universe_every: timedelta = None. When set, the engine re-evaluates the candidate universe on that cadence (e.g. daily).
• Best-effort partial-data handling: a single failed fetch_ohlcv for one symbol must not kill the iteration; that symbol's row becomes NaN and is masked out by Filter automatically.
• Cross-market order routing in the order layer so a pipeline universe spanning BITVAVO + BINANCE can place orders on the right portfolio. (Likely its own sub-issue if it grows.)

Supported envelope (v1)

Timeframe	Max universe
daily	50
< daily	not supported

Above 50 symbols at daily, or any sub-daily timeframe, the engine raises at strategy registration.

Out of scope

• Sub-daily live pipelines.
• Universes > 50 symbols.
• Sector/industry classifiers (no live data source available).

Done when

• Live paper-trading run with a 20-symbol momentum screener pipeline executes for ≥ 24h without error.
• Symbol delisting mid-run is handled gracefully (logged, masked, no crash).

[MDUYN]

Shipped via #515 (consolidates #508). Phase 3a (warmup validation), 3b (live envelope ≤50 daily), 3c (refresh_universe_every cache), and 3d (per-pipeline resilience) are merged on dev.

Async CCXT fetch and cross-market order routing were split out as planned and are tracked in #510.