feat: read-only FastAPI dashboard with 7 API endpoints (issue #96)

Add observability dashboard: status, playbook, scorecard, performance,
context browser, decisions, and active scenarios endpoints.
SQLite read-only on separate connections from trading loop.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -9,6 +9,7 @@ dependencies = [
     "pydantic-settings>=2.1,<3",
     "google-genai>=1.0,<2",
     "scipy>=1.11,<2",
+    "fastapi>=0.110,<1",
 ]
 
 [project.optional-dependencies]