feat: add AWS Bedrock as a model provider

[cport1]

Summary

Adds AWS Bedrock as a model provider, alongside Anthropic, OpenAI, and Ollama.

It uses the model-agnostic Bedrock Converse API (@aws-sdk/client-bedrock-runtime), so any Converse-capable model works — Anthropic Claude, Meta Llama, Amazon Nova/Titan, Mistral, Cohere, etc.

Details

• BedrockTranslator built on the existing BaseTranslator abstraction, reusing the shared prompt-building, JSON parsing, batching, rate limiting, and retry logic.
• Auth: requires aws-region; explicit aws-access-key-id / aws-secret-access-key / aws-session-token are optional and fall back to the default AWS credential chain (so aws-actions/configure-aws-credentials / OIDC just works).
• New action inputs: aws-region, aws-access-key-id, aws-secret-access-key, aws-session-token.
• Default model anthropic.claude-3-haiku-20240307-v1:0; added bedrock rate limits.
• AWS error names/status codes mapped to the repo's AuthenticationError / RateLimitError / retryable TranslatorError.

Usage

```yaml

• uses: aws-actions/configure-aws-credentials@v4
  with:
  role-to-assume: arn:aws:iam::…:role/bedrock-translate
  aws-region: us-east-1
• uses: i18n-actions/ai-i18n@v0.9
  with:
  provider: bedrock
  aws-region: us-east-1
  model: anthropic.claude-3-haiku-20240307-v1:0
  target-languages: de,fr,es
  files: 'src/locales/**/*.xliff'
  ```

Tests

• New BedrockTranslator unit tests (mocked AWS SDK): default model, credential wiring, Converse response parsing, and error mapping.
• New factory test covering all providers.
• Bedrock cases added to config schema tests.
• Full suite: 236 tests, 18 suites — type-check, lint, prettier all green. dist/ rebuilt.