docs: sync documentation with latest codebase state (merged)

- Update Activity Log with 108 missing commits (48 backend + 60 frontend)
- Update version references: backend v2.8.79, frontend v2.8.94
- Update migration count: 18 migrations (0000-0017)
- Update Telegram Mini App Flow to v2.8.94
- Update Payment Flow - Scanner to 2026-06-05
- Update all architectural and database references
- Add MongoDB removal handoff document with updated versions

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

.obsidian/graph.json

@@ -17,6 +17,6 @@
   "repelStrength": 10,
   "linkStrength": 1,
   "linkDistance": 250,
-  "scale": 0.5219627776444189,
+  "scale": 0.27561052639457884,
   "close": true
 }