Add AI chat with skills management and model provider settings

- Model providers for OpenAI and Anthropic message formats (e.g. via
  Sub2API), with API keys encrypted at rest and never returned
- Skills tree with markdown editing, priorities, drafts, publishing and
  rollback; only published skills enter the chat prompt
- Chat page with tool calls over collected news and Binance USD-M
  klines, a persisted CONTEXT.md, reset, and stop-generation support
- Chat may only create skill drafts and update CONTEXT.md; publishing,
  deleting, moving and priority changes stay with the user

web/package.json

@@ -14,12 +14,14 @@
     "dayjs": "^1.11.23",
     "element-plus": "^2.14.7",
     "klinecharts": "^10.0.3",
+    "markdown-it": "^15.0.2",
     "pinia": "^4.0.3",
     "vue": "^3.5.43",
     "vue-router": "^5.4.0"
   },
   "devDependencies": {
     "@antfu/eslint-config": "^9.5.1",
+    "@types/markdown-it": "^14.2.0",
     "@types/node": "^26.6.5",
     "@vitejs/plugin-vue": "^6.0.10",
     "eslint": "^10.12.0",