Implement first analytics report generation #46

Goal

Implement the first analytics report generation workflow for ARGUS.

Why

ARGUS should be able to turn selected market data, metrics and charts into a reusable report. This makes the project more useful for analysis, sharing and future AI-assisted summaries.

Scope

• Generate a first report from selected historical data
• Include core Sprint 2 metrics:
  • cumulative return
  • strongest / weakest movement
  • rolling volatility
• Include basic metadata:
  • selected asset or currency pair
  • date range
  • data source
• Use the report format selected in the research ticket
• Add a simple way to trigger report generation from the NiceGUI dashboard
• Keep report generation separate from UI code
• Document usage

Acceptance criteria

• Report can be generated from analytics data
• Report includes selected metrics
• Report includes metadata
• Report generation can be triggered from NiceGUI
• Report logic is separated from UI code
• Output file is saved or displayed clearly
• Basic tests or verification steps exist
• Existing tests still pass