Add concept overview for Google suite hub

[mattiluki]

Summary

• add README describing the planned 4-in-1 dashboard for Gmail, Tasks, Calendar, and Habits
• outline OAuth setup, API scopes, and backend flow requirements
• include checklist and data model notes for future implementation

Testing

• not run (documentation-only changes)

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Request offline consent before expecting refresh tokens

The minimal OAuth flow instructs calling Google’s authorization URL with only the three API scopes (lines 31‑34) yet step 2 assumes the code exchange will yield refresh tokens. For Google web apps, a refresh token is only issued when the initial authorize request includes offline consent parameters (e.g., access_type=offline and, after first grant, prompt=consent); otherwise you only receive a short‑lived access token and the later persistence/refresh logic cannot work. Please add the offline consent flags to the authorize step so refresh tokens are reliably returned.

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