feat(foxbit): add X-FB-CLIENT identification headers

[matheus-alcuri-foxbit]

Summary

Sends X-FB-CLIENT: ccxt and X-FB-CLIENT-VERSION: <ccxt version> on every foxbit REST request so the exchange can identify and measure ccxt-originated traffic (client header approach chosen over User-Agent, which users/base code can override).

Since the library version constant was not reachable from transpiled exchange code, this adds a getCcxtVersion() base helper implemented above the transpile marker (hand-written per language: TS/JS, Python, PHP, C#, Go, Java). Headers are injected in sign() (same pattern as bybit's Referer), so they take precedence over user headers overrides. A testFoxbit broker-id test asserts both headers via last_request_headers.

Tests run

• eslint (via the use-typescript6 wrapper) — 0 errors on edited files
• npm run tsBuild — pass (after emitAPITs)
• id-tests (brokerId suite incl. new testFoxbit) — passed in JS and Python
• go build (v4 + v4/pro) — pass
• dotnet build cs/ccxt.sln — 4 projects, 0 errors (.NET 10 SDK)
• php -l on edited/regenerated files — clean (php:8.2 container)
• Java compile — not run locally (needs JDK 21+); the helper mirrors adjacent hand-written methods in BaseExchange.java and returns Version.VERSION
• Live smoke (previous round, same code): fetchTicker BTC/BRL — request carried both headers, 200 OK

Notes

• Diff is source-only (9 files, +60/−1): ts/src/** + hand-written base files. Per-exchange generated files are left to the build automation.
• The version header value comes from each language's existing version constant, all already bumped by vss.
• Replaces the equivalent branch/PR from the previous fork repository.