feat: Overload Panel redesign, monitoring factor support, and backend overload detection

[marota]

Summary of changes (commits 94e232c and d430310):

• New OverloadPanel component (frontend/src/components/OverloadPanel.tsx): A compact panel at the top of the left sidebar showing overloaded lines for both N-state and N-1 (post-contingency) states, with clickable line names that zoom the diagram.

• monitoringFactor setting: Exposes MONITORING_FACTOR_THERMAL_LIMITS (default 0.95) as a user-configurable setting, sent to the backend on every config/analysis request.

• Backend overload detection (recommender_service.py): New _get_overloaded_lines() method that compares current flows against thermal limits scaled by monitoring_factor. Both /api/network-diagram and /api/n1-diagram now return a lines_overloaded list. The base network diagram also runs an AC load flow first so annotations are current.

• Rho values scaled by monitoring factor: rho_before, rho_after, and max_rho in enriched action data are now multiplied by monitoring_factor before being sent to the frontend.

• Severity thresholds use monitoring factor: Action card color coding in ActionFeed dynamically uses monitoringFactor instead of hardcoded 1.0/0.9 thresholds.

• View mode toggle relocated: The Flows / Δ Flows toggle moved from ActionFeed to VisualizationPanel.

• standalone_interface.html parity: All changes mirrored in the standalone interface.

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You can create the PR at: https://github.com/marota/ExpertAssist/compare/master...claude/create-pull-request-2dI9g