Add OpenRouter model release dates

[nightt5879]

Closes #3143

Summary

• map OpenRouter model created timestamps into release_date metadata
• add coverage for OpenRouter model catalog release dates

Impact

OpenRouter-backed models returned by /puterai/chat/models/details can now include the same release_date field that other providers expose, using the API-provided creation timestamp formatted as YYYY-MM-DD.

Validation

• npm run test:backend -- src/backend/drivers/ai-chat/providers/openrouter/OpenRouterProvider.test.ts - 1 file passed, 15 tests passed
• npm run build:ts - passed
• git diff --check - passed

[CLAassistant]

All committers have signed the CLA.

[reynaldichernando]

hi @nightt5879 , thank you for the PR, have you tested that it works with the real API?

[nightt5879]

@reynaldichernando
Yes, I tested this against the real OpenRouter /models API.

I checked the DeepSeek V4 models from the live OpenRouter model catalog and confirmed their created timestamps are mapped to release_date correctly:

• deepseek/deepseek-v4-pro -> 2026-04-24
• deepseek/deepseek-v4-flash:free -> 2026-04-24
• deepseek/deepseek-v4-flash -> 2026-04-24

[reynaldichernando]

can confirm its working, and tests are passing

will let @ProgrammerIn-wonderland merge this