feat: integrate AWS Bedrock native embeddings (Titan + Cohere)

[yugborana]

Pull Request Type

• [yes ] ✨ feat (New feature)
• 🐛 fix (Bug fix)
• ♻️ refactor (Code refactoring without changing behavior)
• 💄 style (UI style changes)
• 🔨 chore (Build, CI, maintenance)
• 📝 docs (Documentation updates)

Relevant Issues

resolves #3203

Description

This feature enables users to leverage AWS Bedrock's powerful embedding models natively within AnythingLLM, decoupling embeddings from the general LLM configurations.

Key Additions:

• Dynamically detect and switch request payload shapes for either Titan (inputText) or Cohere (texts/input_type) based on the user's provided Model ID.
• Seamless authentication through API Keys, Session Tokens, or strict IAM / IAM Role permissions.
• Frontend Settings component designed exclusively for configuring AWS Bedrock Vector Engine.
• Updated environment schemas (updateENV, systemSettings) to securely persist configuration elements to the local database.

Visuals (if applicable)

Additional Information

Developer Validations

• [yes ] I ran yarn lint from the root of the repo & committed changes
• Relevant documentation has been updated (if applicable)
• I have tested my code functionality
• Docker build succeeds locally

[yugborana]

@timothycarambat