ARCHITECTURE.md (storage/state lifecycle)

[nanaf6203-bit]

Problem Statement
The README contains a "Contract Architecture" ASCII diagram, but there
is no formal document on storage layout, state transitions, and the
lifecycle of an address from stranger → tipper → tipper+recipient
→ unregistrant.

Why it matters
Auditors and integrators benefit from a single diagram-rich doc
summarizing state machine + storage keys + transition triggers.

Acceptance Criteria

• New docs/ARCHITECTURE.md with:
  • Mermaid state diagram
  • Storage key table
  • Cross-cutting invariants list
• Linked from README.

Files/Modules Likely Affected

• docs/ARCHITECTURE.md (new)
• README.md

Difficulty Medium. Estimated Effort M.

Labels
area:documentation, priority:medium

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Imported from docs/open-issues-draft.md as draft issue #54 (commit 7becd4b). Original draft-order cross-references in this body have been remapped to current GitHub issue numbers at import time.

[GBOYEE]

Hi team — I'd like to take this on as part of the GrantFox campaign. I'll implement it and open a PR referencing this issue shortly.

[Hicent2]

hello, please can i work on this

[grantfox-oss]

🦊 GrantFox — @Hicent2 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #114)
2. Your PR will be reviewed by the StellarTips maintainers

Good luck! Track your progress on GrantFox.