This commit marks a major streamlining of the Tad project, focusing on the core desktop application and removing experimental features. The primary goal is to simplify the codebase, improve maintainability, and focus development on the parts of the application I personally find the most valuable.

Key changes in this commit:

- **Remove Unused Database Backends:** The `reltab-aws-athena`, `reltab-bigquery`, and `reltab-snowflake` packages have been removed. The project now exclusively uses `reltab-duckdb`, which provides excellent performance for the desktop application and I don't really intend to maintain these packages.

- **Remove Web Deployment Packages:** The `tadweb-app` and `tadweb-server` packages, which were used for web-based deployment, have been removed to focus on the Electron-based desktop app. I personally don't think that should be a focus of this project, in my opinion duckdb's web-ui extension is where that kind of feature should live.

- **Migrate to GitHub Actions:** The CI/CD pipeline has been migrated from Azure Pipelines (`azure-pipelines.yml`) to GitHub Actions (`.github/workflows/build.yaml`).

- **Simplify Build Process:** Various build scripts in the `tools/` directory have been removed or simplified. The build process is now more straightforward and easier to maintain.

- **Code and Configuration Cleanup:** Numerous `package.json`, `tsconfig.json`, and other configuration files have been updated to remove references to the deleted packages and to align with the new project structure.

⚠️ **NOTE:** I used an LLM agent for some of the more tedious changes
while upgrading lerna, hopefully there weren't too many mistakes