Build universal database explorer

[kkopanidis]

**What kind of change does this PR introduce?** (check at least one)

- [ ] Bugfix
- [x] Feature
- [ ] Code style update
- [ ] Refactor
- [ ] Build-related changes
- [ ] Other, please describe:

**Does this PR introduce a breaking change?** (check one)

- [ ] Yes
- [x] No

If yes, please describe the impact and migration path for existing applications:

**The PR fulfills these requirements:**

- [x] It's submitted to the `master` branch
- [ ] When resolving a specific issue, it's referenced in the PR's title (e.g. `fix #xxx`, where "xxx" is the issue number)

If adding a **new feature**, the PR's description includes:
- [x] A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

**Other information:**
This PR introduces a comprehensive Database Explorer module, providing a unified interface for interacting with both MongoDB and SQL databases (PostgreSQL, MySQL, SQLite). This feature significantly enhances the platform's data management capabilities by allowing users to:

-   **Manage Connections:** Create and manage connections to various database types.
-   **Explore Data:** Browse database objects (tables, collections, views) and view their contents.
-   **Build & Execute Queries:** Visually construct and execute queries for both SQL and MongoDB, or use a custom query editor.
-   **Inspect Schema:** View detailed schema information, including fields, types, constraints, and indexes.
-   **Visualize Results:** Display query results in various chart formats (table, bar, pie, line) with filtering and sorting options.

This explorer is a crucial tool for developers and administrators, streamlining database interaction and analysis directly within the application. It lays a solid foundation for future enhancements like advanced query history, data editing, and more sophisticated visualizations.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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