feat(matrix-skilltree-bot): add Matrix bot for skill tree and XP management

- Skill management: create, list, view details, delete
- XP tracking with level-up notifications
- Branch filtering (intellect, body, creativity, social, practical, mindset, custom)
- Activity history per skill or global
- User statistics (total XP, skill count, highest level, streak)
- German/English command aliases
- Number-based reference system for ease of use
- JWT auth via mana-core-auth
- Health check endpoint on port 3326

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/matrix-skilltree-bot/.env.example

@@ -0,0 +1,15 @@
+# Server
+PORT=3326
+
+# Matrix
+MATRIX_HOMESERVER_URL=http://localhost:8008
+MATRIX_ACCESS_TOKEN=syt_xxx
+MATRIX_ALLOWED_ROOMS=#skilltree:matrix.mana.how
+MATRIX_STORAGE_PATH=./data/bot-storage.json
+
+# Skilltree Backend
+SKILLTREE_BACKEND_URL=http://localhost:3024
+SKILLTREE_API_PREFIX=/api/v1
+
+# Mana Core Auth
+MANA_CORE_AUTH_URL=http://localhost:3001