feature #589 [AI Bundle] Use stringNode() and integerNode() for string configuration values (OskarStark)

This PR was squashed before being merged into the main branch.

Discussion
----------

[AI Bundle] Use `stringNode()` and `integerNode()` for string configuration values

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| Docs?         | no
| Issues        | --
| License       | MIT

Replace `scalarNode()` with more specific node types for better configuration type validation:

- Use `stringNode()` for string values (API keys, URLs, service names, etc.)
- Use `integerNode()` for integer values (dimensions, etc.)
- Keep `scalarNode()` only for mixed-type fields where appropriate

This provides better type validation and makes the configuration more self-documenting.

## Changes Made

- **String fields**: API keys, URLs, endpoints, service names, class names, database/collection names, etc. now use `stringNode()`
- **Integer fields**: `dimensions` and `top_k` fields now use `integerNode()`
- **Mixed fields**: Strategy, metric, and similar fields remain as `scalarNode()`

## Needs
- [ ] #277

Commits
-------

492f75f [AI Bundle] Use `stringNode()` and `integerNode()` for string configuration values

Author: OskarStark