fix: remove unused pandas-ta dependency causing Python version conflict

pandas-ta requires Python>=3.12 but was listed as a dependency despite
not being imported anywhere in the codebase. The trading_mcp.py and
feature_extraction_mcp.py modules use manual implementations for all
technical indicators.

- Remove pandas-ta from pyproject.toml dependencies
- Update misleading docstring in trading_mcp.py
- Regenerate uv.lock

backend/mcp_servers/trading_mcp.py

@@ -1,7 +1,7 @@
 """Trading MCP Server.
 
 This MCP server provides technical analysis indicators and signals.
-Uses pandas_ta for technical indicator calculations.
+Uses manual implementations for technical indicator calculations.
 """
 
 import logging

pyproject.toml

@@ -45,8 +45,7 @@ dependencies = [
     # Export & Reporting
     "reportlab>=4.0.0",
     "pypdf>=3.17.0",
-    # Feature Engineering
-    "pandas-ta>=0.3.14b",
+    # Feature Engineering (manual implementations used instead of pandas-ta)
     "PyWavelets>=1.4.1",
     "scikit-learn>=1.3.0",
     # ML Models (P1 - Optional)