📝 Architecture documentation

[MaxieHelenBichmann]

Description

• Improve the structure of documentation:
  • separation of modular paper-focused "tools" and more infrastructure-related information "user guide"
  • classifcation of modular tools in categories Synthesis, State Preparation, Decoders, Compilation (potentially better naming/classification possible)
• Add basic architecture/workflow documentation.
• Some bug fixes w.r.t. incorrect references to the installation page.

Fixes #784

Assisted-by: Codex for build pipeline summarization, first reviewer

Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
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• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

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[lsschmid]

I renamed and re-ordered the sections a little: state preparation now lives under Circuit Synthesis rather than being its own category, and Compilation is now Logical Compilation.