Add email ownership architecture plan

[nonggde]

Closes #434

Summary

• add a folder-local Email Ownership Tracker architecture plan covering public API, types, services, guards, hooks, components, fixtures, tests, and docs
• add data boundary notes for owned data, product-owned systems, dependency limits, and future adapter handoff rules
• add a module-map fixture plus Node architecture test to verify folder scope, required layers, forbidden app areas, and contributor change rules

Scope

• only touches tools/v1/team/email-ownership-tracker/
• no app shell, dashboard, routing, inbox architecture, mail rendering, auth, wallet, Stellar, database, notification, provider, analytics, or design-system integration
• no production data, live network calls, server persistence, secrets, webhooks, background jobs, mailbox mutation, ownership writes, or paid services
• avoids the old closed [V1][team] Email Ownership Tracker - Architecture and folder contract #434 attempt paths: README.md, specs.md, docs/ARCHITECTURE.md, docs/CONTRIBUTOR_BOUNDARY.md, and tests/architecture-contract.test.mjs

Validation

• node --test tools/v1/team/email-ownership-tracker/tests/architecture-plan.test.mjs
• npx --yes prettier --check tools/v1/team/email-ownership-tracker/docs/ARCHITECTURE_PLAN.md tools/v1/team/email-ownership-tracker/docs/DATA_BOUNDARIES.md tools/v1/team/email-ownership-tracker/fixtures/architecture-module-map.json tools/v1/team/email-ownership-tracker/tests/architecture-plan.test.mjs
• git diff --cached --check
• ASCII scan over changed Email Ownership Tracker architecture files

Notes

• this is a self-contained architecture contract only; future feature, UI, security, or integration issues can add implementation files behind these documented boundaries