initial commit — cassandra v0.1

Containerised macro-strategy dashboard: 4-panel web UI (indicators,
portfolio, flash news, AI strategic log), MariaDB store, hourly
ingestion jobs, OpenRouter-backed AI analysis.

Ports the four prototype scripts in the parent dir (market_pulse,
flash_news, trading212, strategic_log) into async services backed by a
persistent DB and served via FastAPI + Jinja2 + HTMX. APScheduler runs
as a separate compose service for crash-safety and easier restarts.

Portfolio composition + position names come live from Trading 212;
news per-ticker headlines reuse those names. Tone (NOVICE/INTERMEDIATE/
PRO) and analysis style (DRY/SPECULATIVE) are env-configurable and
stored on each log row so historical entries show what produced them.

Default model is deepseek/deepseek-v4-flash (overridable via env).
Light/dark theme toggle, sans-serif for prose surfaces, monospace for
data. Bearer-token auth, OpenRouter monthly cost cap, RSS feeds auto-
disabled on consecutive failures.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/db.py

@@ -0,0 +1,55 @@
+"""Async DB engine, session factory, declarative base, UTC helper."""
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import AsyncIterator
+
+from sqlalchemy.ext.asyncio import (
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import get_settings
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+_engine = None
+_session_factory: async_sessionmaker[AsyncSession] | None = None
+
+
+def utcnow() -> datetime:
+    """All timestamps in Cassandra are tz-aware UTC by convention."""
+    return datetime.now(timezone.utc)
+
+
+def get_engine():
+    global _engine
+    if _engine is None:
+        s = get_settings()
+        _engine = create_async_engine(
+            s.DATABASE_URL,
+            pool_pre_ping=True,
+            pool_recycle=3600,
+            future=True,
+        )
+    return _engine
+
+
+def get_session_factory() -> async_sessionmaker[AsyncSession]:
+    global _session_factory
+    if _session_factory is None:
+        _session_factory = async_sessionmaker(
+            get_engine(), expire_on_commit=False, class_=AsyncSession
+        )
+    return _session_factory
+
+
+async def get_session() -> AsyncIterator[AsyncSession]:
+    """FastAPI dependency yielding an async session."""
+    async with get_session_factory()() as session:
+        yield session