feat: Circulation of Love — anonymous, time-bound letter sharing

[TrainTravel]

Summary

Implements Circulation of Love — an opt-in surface where users share anonymous, time-bound letters in their primary language. Letters drift through a current visible to opted-in users in the same language for 7–30 days, then archive.

Philosophy: Inspired by the user's grandfather's idea of the circulation of love. Not a social network (no follows, profiles, replies, comments). The only reaction is "Hold this for a moment" — silent, idempotent, private to the author.

What's Included

Spec & Design — full spec in docs/specs/love-circulation.md + Lovable display prompt in docs/launch/lovable-circulation-display.md

Data Layer:

• 3 tables: love_letters, letter_holdings, circulation_settings + full RLS (authors always see own letters; others only see passed+live+matching-language IF opted in)
• Per-language pseudonym pools (16–20 natural-imagery names) + deterministic FNV-1a hash
• Hooks: usePseudonym, useCirculationSettings, useLoveLetters

Edge Functions:

• moderate-letter — Gemini 2.5 Flash pre-publish moderation (wide pass, softfail on ambiguous self-harm/PII, block on explicit harm/harassment)
• circulate-letters — cron-style archival sweep (authenticated by CIRCULATION_CRON_SECRET)

UI (3 screens):

• LettersInCirculationScreen — drift feed + Join CTA for non-opted-in
• ShareALetterScreen — 500-char compose + pseudonym chip + softfail/block note rendering
• CirculationSettingsScreen — receive/share toggles + 7/14/30 TTL chooser

Wiring:

• 3 new JournalSteps, 3 new navigation openers on useJournal, Waves-icon tile on HomeScreen
• animate-letter-drift keyframe (12s sine-like motion, respects prefers-reduced-motion)
• Full bilingual coverage en/fr/es/ja/zh-Hans/zh-Hant

Tests:

• 11 unit tests (pseudonym determinism, pool integrity, language-specific selection)
• 5 E2E specs (navigation, CTA visibility, settings flow, TTL chooser)

Bug Fixes (from test validation)

• 🟡 E2E auth setup: Added injectMockSession() + mockAuthRoutes() to beforeEach; all 5 circulation E2E specs now pass
• 🟡 Language filter: Added .eq('language', primaryLang) to useLoveLetters.refresh() — users now only see letters in their primary language

Test Plan

• ✅ vitest: 359 pass (32 files)
• ✅ E2E: 5 pass in circulation.spec.ts
• ✅ tsc: clean (0 errors)
• ✅ Lint: no new issues

Manual verification needed:

1. Opt in to Circulation → share a letter → verify pseudonym is stable, single regenerate works, moderation verdicts render correctly
2. Switch primary language → verify feed shows only letters in new language
3. Hold a letter → unhold → verify idempotency (duplicate holds don't error)
4. Drift animation → verify smooth loop, staggered delays, respects prefers-reduced-motion

Pre-deployment checklist:

• Deploy edge functions: supabase secrets set CIRCULATION_CRON_SECRET=... + supabase functions deploy moderate-letter circulate-letters
• Schedule circulate-letters cron (daily archival sweep)
• Lovable visual pass (paste docs/launch/lovable-circulation-display.md into Lovable for feed aesthetics)

🧠 Generated with Claude Code