Implement Community Gratitude Board, CBT SMER Diary, and Version Bump to v1.21.0

[mx57]

Cycle 21 updates introducing highly interactive social and AI features:

1. Community Gratitude Board: Horizontal pastel sticker-style card list in the Community tab allowing users to share their grateful thoughts and support others (heart reactions trigger +1 Karma with haptics, creating a post gives +15 Karma). All content is automatically run through AI-moderation.
2. AI Coach CBT SMER Cognitive Diary: Active conversational triggers ('смэр', 'дневник смэр', 'когнитивный дневник') starting a highly professional 5-step cognitive therapy questionnaire (Situation, automatic Thoughts, Emotions, Reaction, and Alternative thinking).
3. Tests & Coverage: Full Jest unit coverage in __tests__/Cycle21Improvements.test.ts for CBT exercises and Gratitude board interactions.
4. Screenshots & Visuals: Fresh close-up and full UI screenshots of the Gratitude Board and AI Coach SMER responses have been saved under assets/screenshots/.
5. Releases: Bumped app versions to v1.21.0 for subsequent APK building.

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PR created automatically by Jules for task 28162124150789906 started by @mx57

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