docs: Add navigation structure and remove redundant topics

[vnikolova]

Description

The changes introduced in this PR improve the navigation and structure of the Docs by doing the following:

1. Splitting the Database and Datasource topic:

The single topic Database and Datasource has been separated into two distinct topics: Working with Databases and Working with Datasources.

These topics previously existed but were not included in the Table of Contents (TOC). I have updated them with relevant content migrated from the original Database and Datasource section. Please review to ensure that all transferred information is accurate and complete.

2. Replacing the Samples topic with an external link
3. Using the show-structure element to display sub-sections in the right-side navigation for each topic
4. Consistent formatting

• Removed 'Overview' chapter headings
• Adjusted heading and note formatting

Type of Change

• Documentation update

Checklist

• Unit tests are in place
• The build is green (including the Detekt check)
• All public methods affected by my PR has up to date API docs
• Documentation for my change is up to date

[bog-walk]

@vnikolova Looks good, just a couple comments about links I noticed.