[Dashboard]: Add learning curves display as graphs

[ApusBerliozi]

Summary

I think it would be cool to display learning results as graphs (in fenn style), so users can have more convenient view on whole learning process. It would be cool to have a separate tab for them in session, which fills with related graphs as the calculation completes

Scope

• Add a "graphs" tab into session
• Add Loss curve, Metric curve and Learning rate curve
• Render these curves after the whole calculation process
• Design them in fenn-colours style
• Update README and docs

Acceptance Criteria

• Users have "graphs" tab in their session
• Users can check Loss curve, Metric curve and Learning rate curve
• Graphs rendered after calculation completes
• Graphs designed in fenn-colours
• README and docs are updated

Parent Issue

#98

[AaronProbha18]

hey @ApusBerliozi,
I'd like to work on this issue, let follow the sub issue pattern here as well considering this is sort of a big issue?

Plan

The codebase currently lacks a way to track structured numeric data during training. To solve this, I'll introduce a metric-logging API that writes data into the .fn file. The dashboard will then parse these metrics and display them in a new "Graphs" tab.

I'll start with the backend by modifying the logger and scanner, then move to the frontend to build the UI tabs and SVG line charts. Building hand-rolled SVGs is a great design choice here as it avoids adding any third-party JavaScript dependencies, preserving the current vanilla setup. I am assuming a step parameter makes sense for the chart x-axes, and that we can leverage the frontend's existing auto-reload cycle to render the metrics once a session transitions away from a running state.

Changes

• fenn/logging.py: Add a log_metric method to securely append <metric> XML elements alongside standard text entries.
• fenn/dashboard/scanner.py: Extract the new <metric> nodes during file parsing and attach them to the returned SessionData.
• fenn/dashboard/types.py: Define a MetricPoint TypedDict and update the SessionData contract to type-check the new data.
• fenn/dashboard/app.py: Verify that metrics automatically flow through the session endpoint, while ensuring they are properly stripped from the lightweight /api/sessions listing.
• fenn/dashboard/templates/session.html: Wrap the existing log views in a tabbed layout and create a new panel with placeholder containers for the charts.
• fenn/dashboard/static/app.js: Implement tab-switching logic and an SVG rendering helper that parses the session data and hooks naturally into the existing refresh() loop.
• fenn/dashboard/static/style.css: Style the tab navigation and chart cards using existing theme variables.
• tests/unit/dashboard/test_api.py: Add tests to verify metric parsing and guarantee backward compatibility for files without metrics.

[ApusBerliozi]

Hey @AaronProbha18! Sure thing mate, let's decompose this one as well. Assigned the issue to ya :)

[AaronProbha18]

thanks my guy!
I think these 3 issues would be good enough to cover the entire scope