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/utils/safe_float.py

@@ -0,0 +1,88 @@
+"""Numeric safety utilities for the ATLAS Terminal backend.
+
+Provides safe type-coercion helpers used across all services to handle
+None, NaN, and non-numeric values gracefully without raising exceptions.
+"""
+
+from typing import Optional
+
+import pandas as pd
+
+
+def _safe_float(x: object) -> Optional[float]:
+    """Convert *x* to ``float``, returning ``None`` for unconvertible values.
+
+    Handles ``None``, ``NaN`` (both Python ``float('nan')`` and pandas
+    ``pd.NA``), and arbitrary objects whose ``float()`` conversion fails.
+
+    Parameters
+    ----------
+    x:
+        Any value that might be numeric.
+
+    Returns
+    -------
+    Optional[float]
+        The float representation, or ``None`` if conversion is impossible.
+    """
+    if x is None or (isinstance(x, float) and (x != x or pd.isna(x))):
+        return None
+    try:
+        return float(x)
+    except (TypeError, ValueError):
+        return None
+
+
+def _na(x: object) -> object:
+    """Return the string ``'N/A'`` for ``None``/``NaN``, otherwise *x* unchanged.
+
+    Useful when building display-ready dictionaries or DataFrames where
+    missing numeric values should appear as a human-readable sentinel.
+
+    Parameters
+    ----------
+    x:
+        Any value.
+
+    Returns
+    -------
+    object
+        ``'N/A'`` when *x* is ``None`` or ``NaN``; *x* otherwise.
+    """
+    if x is None or (isinstance(x, float) and (pd.isna(x) or x != x)):
+        return "N/A"
+    return x
+
+
+def _format_shares_display(shares: Optional[float]) -> str:
+    """Format a share count for human-friendly display.
+
+    Examples
+    --------
+    >>> _format_shares_display(15_420_000_000)
+    '15.42B Shares'
+    >>> _format_shares_display(1_200_000)
+    '1.20M Shares'
+    >>> _format_shares_display(None)
+    'N/A'
+
+    Parameters
+    ----------
+    shares:
+        Raw share count (absolute number, not in millions/billions).
+
+    Returns
+    -------
+    str
+        A concise string such as ``'15.42B Shares'`` or ``'N/A'``.
+    """
+    if shares is None or shares <= 0:
+        return "N/A"
+    s = float(shares)
+    if s >= 1e9:
+        return f"{s / 1e9:.2f}B Shares"
+    if s >= 1e6:
+        return f"{s / 1e6:.2f}M Shares"
+    if s >= 1e3:
+        return f"{s / 1e3:.2f}K Shares"
+    return f"{s:.0f} Shares"