Add T-Systems LLMHub as a provider

Request

Add T-Systems AI Foundation Services (LLMHub) as a new provider in models.dev.

Why

T-Systems LLMHub is a GDPR-compliant, EU-hosted LLM gateway run by Deutsche Telekom's enterprise IT subsidiary. It exposes 38 models — a mix of frontier proprietary models (OpenAI, Anthropic, Google, Mistral) and open-weight models hosted on T-Cloud Germany (Llama, Qwen, GPT-OSS, Teuken). It is widely used by European enterprises that need EU data residency for AI workloads, and currently has no entry in models.dev.

Provider details

• Name: T-Systems AI Foundation Services
• API: OpenAI-compatible — https://llm-server.llmhub.t-systems.net/v2
• SDK: `@ai-sdk/openai-compatible`
• Auth: `T_SYSTEMS_API_KEY`
• Docs: https://docs.llmhub.t-systems.net/
• Model catalog & pricing: telekom/aifoundation-docs (Standard1000 plan tier)

Proposed model coverage (38 total)

Status

Implementation submitted in PR #1383. The PR uses `extends` (README rule 3a) for 26 of 38 wrapper models, inheriting from canonical definitions in `providers/{anthropic,openai,google,mistral,llama,alibaba}/` with T-Systems pricing markup as local overrides. Validation passes (`bun run validate`) and `bun run compare:migrations` shows zero diff for the conversions.

Start by reviewing PR #1383 and the canonical provider definitions under providers/{anthropic,openai,google,mistral,llama,alibaba}/. Run bun run validate and bun run compare:migrations to verify the provider and model catalog; done means validation passes and the migration comparison has zero diff.