fix(bedrock): improve AWS credential handling and add model definitions

- Change error to warning when AWS credentials are missing in environment
- Allow fallback to system configuration (aws config files or instance profiles)
- Remove hardcoded region and profile parameters in Bedrock client
- Add Claude 3.7 Sonnet and DeepSeek R1 model definitions for Bedrock
- Update config manager to properly handle Bedrock provider

tests/unit/config-manager.test.js

@@ -266,6 +266,7 @@ describe('Validation Functions', () => {
 		expect(configManager.validateProvider('perplexity')).toBe(true);
 		expect(configManager.validateProvider('ollama')).toBe(true);
 		expect(configManager.validateProvider('openrouter')).toBe(true);
+		expect(configManager.validateProvider('bedrock')).toBe(true);
 	});
 
 	test('validateProvider should return false for invalid providers', () => {