feat(trading): Dhan + Shoonya Indian broker connectors (paper-capped)

[warren618]

Summary

Adds two broker_sdk connectors for the Indian equity and F&O markets (NSE/BSE) — Dhan (dhanhq) and Shoonya / Finvasia (NorenRestApiPy) — following the connector-first architecture. Read access + locally simulated paper-account order placement.

This is a maintainer follow-up to #174 that lands the contribution with the paper/live boundary made structural.

Why capped to paper + read-only

Both brokers expose no sandbox and no runtime paper/live discriminator — a single token / TOTP login reaches the same real account, and "paper" is purely a local simulation flag. That is exactly the case the project already caps at paper + read-only for Longbridge, because every connector that places live orders earns it with a broker-provided discriminator (Tiger 17-digit account · Alpaca host+key separation · OKX demo flag · Binance testnet host · Futu trd_env). Dhan/Shoonya can't provide one, so they follow the Longbridge precedent.

Concretely, vs. the original #174 submission:

• Structural cap. place_order / cancel_order refuse any non-paper config at the first line, so a flipped profile override can never reach a live order. No *-live-trade profile is registered — three profiles each (paper-sdk read-only · paper-trade local-sim · live-sdk-readonly read-only), mirroring Longbridge.
• Removed a crash. The original live path set an invalid asset class (in_equity, not a member of AssetClass) that raised ValueError for every order through the gate; that mapping is dropped.
• Wired the classifier. DHAN_TOOL_CLASS / SHOONYA_TOOL_CLASS are now registered in the live classifier registry (they were defined but never imported).
• Hardening. Order ops pinned WRITE; secrets redacted; pyotp made an optional dependency with a clean error; Shoonya sessions cached per user_id to avoid cross-account reuse; dead code removed.

What you get

Real-time NSE/BSE data, account/position/order reads (paper + live read-only), and local paper-strategy simulation. Live order placement stays off by construction; if either broker ships a real sandbox/demo endpoint later, a discriminator can be added and the cap lifted cleanly.

Tests

pytest — 2998 passed, 2 skipped (CI-equivalent run). New coverage in test_sdk_connectors.py:

• profile registration for both connectors
• non-paper config is fail-closed in place_order / cancel_order
• paper config simulates locally
• order ops resolve WRITE through the shared classifier + registry
• secret redaction
• regression guard: no-discriminator brokers (Longbridge, Dhan, Shoonya) never expose a *-live-trade profile

Original connector work by @panditvirchandra77-lgtm (#174).