Disable SSL verify for yfinance via curl_cffi session

Live server sits behind a TLS-inspecting proxy that re-signs HTTPS with
an untrusted root CA, breaking yfinance HTTPS calls. yfinance >= 0.2.40
requires a curl_cffi session (rejects requests.Session), so we build
one with verify=False and impersonate=chrome.

Trade-off: yfinance traffic is no longer authenticated against MITM.
Acceptable because the data is public market quotes and an attacker
can at worst inject bad prices. Session is yfinance-only and not reused
for any authenticated traffic.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

data_provider.py

@@ -24,6 +24,17 @@ except ImportError:
     yf = None
     _YF_AVAILABLE = False
 
+# Insecure HTTPS session for yfinance — disables SSL verification.
+# Needed on servers behind a TLS-inspecting proxy that re-signs certs with
+# an untrusted root. yfinance requires a curl_cffi session, not requests.
+# Security trade-off: man-in-the-middle attacks on yfinance traffic are
+# possible. Acceptable here because the data is public market quotes.
+try:
+    from curl_cffi import requests as _curl_cffi_requests
+    _YF_SESSION = _curl_cffi_requests.Session(impersonate="chrome", verify=False)
+except ImportError:
+    _YF_SESSION = None
+
 from config import PlatformConfig, Timeframe, SYMBOL_DISPLAY, PIP_VALUES
 
 logger = logging.getLogger(__name__)
@@ -304,10 +315,13 @@ class ForexDataProvider:
             period = "2y"
 
         try:
-            df = yf.download(
+            yf_kwargs = dict(
-                yf_symbol, interval=yf_interval, period=period,
+                interval=yf_interval, period=period,
                 progress=False, auto_adjust=False, threads=False,
             )
+            if _YF_SESSION is not None:
+                yf_kwargs["session"] = _YF_SESSION
+            df = yf.download(yf_symbol, **yf_kwargs)
             if df is None or df.empty:
                 return None