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

backend/pyproject.toml

@@ -8,10 +8,13 @@ authors = [
 requires-python = ">=3.13"
 dependencies = [
     "alembic>=1.20.0",
+    "anthropic>=1.13.0",
     "argon2-cffi>=25.1.0",
     "asyncpg>=0.32.0",
+    "cryptography>=50.0.2",
     "fastapi>=0.143.0",
     "httpx>=0.28.1",
+    "openai>=3.30.0",
     "pydantic-settings>=2.15.0",
     "pyjwt>=2.15.1",
     "redis>=8.1.0",