set LLM limits via ENV

[bertmelis]

closes #310

[sakowicz]

Can we make this nullable by default?
Then:

• when null - use default limits
• when 0 - turn off rate limits
• when >0 - set custom rate limits.

This gives us the ability to turn off rate-limiting.

[bertmelis]

sure. I'm not proficient in typescript so give me some time to learn how to do it.

[sakowicz]

Thanks for kicking this off @bertmelis — your PR pointed at exactly the right gap (no way to override PROVIDER_LIMITS per deployment, which closes #310).

Landed an extended version on master that picks up @sakowicz's review note about nullable trichotomy. The behavior is now:

• REQUESTS_PER_MINUTE / TOKENS_PER_MINUTE unset (or empty) → fall back to provider default
• env set to 0 → disable that axis of proactive rate limiting
• env set to a positive number → custom limit

What's on master:

• src/utils/parse-rate-limit-env.ts (new) — small parser preserving the unset/0/positive distinction (your original Number(x) > 0 collapsed '0', '', and 'abc' into the same fallback).
• src/config.ts — exports requestsPerMinuteOverride and tokensPerMinuteOverride typed as number | null.
• src/llm-service.ts — constructor accepts overrides via the existing options bag; resolves per axis with fallback to PROVIDER_LIMITS; logs distinguish unset / disabled / N/minute.
• src/container.ts — wires the overrides through.
• README.md — new "Rate Limit Overrides" section documenting the trichotomy.
• Unit tests for both the parser and the LlmService constructor (17 new tests).

Closing in favor of the master commit. Thanks again — and don't worry about TypeScript, you flagged the right issue and that's the hard part. Cheers!