feat: add Atlas Terminal — Next.js 14 + FastAPI full-stack migration

Complete migration from Streamlit to Next.js 14 App Router + FastAPI backend.

Frontend (Next.js 14):
- 10 pages: Overview, Research, Valuation, Technical, Markets, Earnings, News, Portfolio, Filings, Settings
- Terminal Noir dark theme with custom Tailwind config
- TradingView Lightweight Charts for candlestick/volume
- Valuation: DCF, Sensitivity Matrix, Monte Carlo, Tornado, Reverse DCF
- Financial Statements table with YoY growth badges and margin rows
- SEC EDGAR inline filing viewer with section tabs
- News split-view with iframe article embedding
- Technical Analysis with RSI, MACD, Bollinger, Fibonacci, Moving Averages
- Earnings beat/miss visualization
- AI Copilot chat panel with Gemini integration

Backend (FastAPI):
- 13 routers: market_data, financials, valuation, technical, earnings, insider, edgar, news, portfolio, analysis, chat, estimates, fx
- Services: DCF engine, Monte Carlo simulation, sensitivity analysis, risk metrics, SEC parser, technical indicators
- yfinance + yahooquery data sources with fallback pattern
- SQLite caching layer

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

atlas-terminal/server/db/database.py

@@ -0,0 +1,122 @@
+"""SQLite database manager for ATLAS Terminal.
+
+Provides async database access via aiosqlite with a singleton connection
+pattern. Replaces the previous Supabase dependency with local-first SQLite.
+"""
+
+import os
+from pathlib import Path
+from typing import Optional
+
+import aiosqlite
+
+# Resolve the database file path relative to this module
+_DB_DIR: Path = Path(__file__).resolve().parent.parent / "data"
+_DB_PATH: str = str(_DB_DIR / "atlas.db")
+
+# Singleton connection holder
+_connection: Optional[aiosqlite.Connection] = None
+
+
+async def get_db() -> aiosqlite.Connection:
+    """Return the singleton async SQLite connection.
+
+    Creates the connection (and the data/ directory) on first call.
+    Enables WAL mode and foreign keys for better concurrency and integrity.
+
+    Returns:
+        An open ``aiosqlite.Connection`` ready for queries.
+    """
+    global _connection
+
+    if _connection is not None:
+        return _connection
+
+    _DB_DIR.mkdir(parents=True, exist_ok=True)
+
+    _connection = await aiosqlite.connect(_DB_PATH)
+    _connection.row_factory = aiosqlite.Row
+    await _connection.execute("PRAGMA journal_mode=WAL")
+    await _connection.execute("PRAGMA foreign_keys=ON")
+
+    return _connection
+
+
+async def init_db() -> None:
+    """Create all application tables if they do not already exist.
+
+    Should be called once during application startup (e.g. in a FastAPI
+    ``lifespan`` handler).
+    """
+    db = await get_db()
+
+    await db.execute(
+        """
+        CREATE TABLE IF NOT EXISTS portfolio_positions (
+            id          INTEGER PRIMARY KEY AUTOINCREMENT,
+            ticker      TEXT    NOT NULL,
+            name        TEXT    NOT NULL,
+            shares      REAL    NOT NULL,
+            avg_cost    REAL    NOT NULL,
+            currency    TEXT    NOT NULL DEFAULT 'USD',
+            broker      TEXT,
+            created_at  TEXT    NOT NULL DEFAULT (datetime('now')),
+            updated_at  TEXT    NOT NULL DEFAULT (datetime('now'))
+        )
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE TABLE IF NOT EXISTS watchlist (
+            id       INTEGER PRIMARY KEY AUTOINCREMENT,
+            ticker   TEXT    NOT NULL UNIQUE,
+            added_at TEXT    NOT NULL DEFAULT (datetime('now'))
+        )
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE TABLE IF NOT EXISTS dashboards (
+            id          INTEGER PRIMARY KEY AUTOINCREMENT,
+            name        TEXT    NOT NULL,
+            layout_json TEXT    NOT NULL,
+            created_at  TEXT    NOT NULL DEFAULT (datetime('now')),
+            updated_at  TEXT    NOT NULL DEFAULT (datetime('now'))
+        )
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE TABLE IF NOT EXISTS settings (
+            key   TEXT PRIMARY KEY,
+            value TEXT NOT NULL
+        )
+        """
+    )
+
+    await db.execute(
+        """
+        CREATE TABLE IF NOT EXISTS cache (
+            key        TEXT PRIMARY KEY,
+            value      TEXT NOT NULL,
+            expires_at REAL NOT NULL
+        )
+        """
+    )
+
+    await db.commit()
+
+
+async def close_db() -> None:
+    """Close the singleton database connection.
+
+    Safe to call even if the connection was never opened.
+    """
+    global _connection
+
+    if _connection is not None:
+        await _connection.close()
+        _connection = None