docs: add comprehensive Workspaces API manual for 3rd party LLM integration

[yustme]

Jira issue(s): PROOF-XXX

Changes:

• Added new documentation page /integrate/storage/api/workspaces/ with comprehensive guide for third-party applications and LLMs to interact with Keboola workspaces
• Updated navigation to include the new Workspaces API page under Integration > Storage > Using API

The documentation covers:

• Prerequisites (Storage API Token, Stack URL)
• Discovering the Workspaces API endpoint via Storage API Index
• Listing workspaces in a project
• Getting workspace details
• Creating workspaces (sync and async)
• Resetting workspace passwords and obtaining credentials
• Setting public keys for key-pair authentication
• Deleting workspaces
• Working with development branches
• Error handling
• Best practices for third-party applications
• Complete Python example workflow

---

Human review checklist:

• Verify API endpoint paths are correct (e.g., /v2/storage/workspaces)
• Verify JSON response formats match actual API responses
• Review the Python example code for correctness
• Check if the /credentials endpoint is available (code shows isAvailableInStorageV1: false)
• Verify branch-aware endpoint format (/v2/storage/branch/{branchId}/workspaces)

Notes:

• Documentation was created by analyzing the connection repo's PHP controllers and client libraries
• The Python example code was not tested against a live API

Link to Devin run: https://app.devin.ai/sessions/af3e31f17b19492f88f2c6f30e223e22
Requested by: Vojta Tuma (@yustme)

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