Refactor InHouseWebBasedGrapher to use MEAPlotter for bar plotting

[Copilot]

NetworkAnalysis/InHouseWebBasedGrapher duplicated bar-chart-with-significance logic that already exists (better) in IPNAnalysis/MEAPlotter. The two separate plot functions also had inconsistent stats (manual per-mean t-test approximation instead of proper t-test / ANOVA+Tukey).

Changes

plot_functions.py

• Drops plot_activity_graphs and plot_bar_with_p_values (~240 lines of bespoke matplotlib + manual stats)
• Adds plot_metrics_graphs — single function delegating to MEAPlotter.plot_bars_by_div():
  • seaborn-based grouped bars + scatter, publication-quality styling
  • 2 groups → independent t-test; 3+ groups → one-way ANOVA + Tukey HSD (via MEAPlotter's centralized stats)
  • adds _fig_to_dash_outputs(fig) helper to convert a matplotlib figure into the (html.Img, svg_bytes, png_bytes) tuple Dash expects
• Keeps plot_activity_graphs / plot_bar_with_p_values as thin backward-compatible aliases
• plot_isi_graph and min_max_normalize unchanged

app_callbacks.py

• Replaces the filename-dispatch (if 'activity' in filename … elif 'networks' in filename) with a single plot_metrics_graphs(…) call
• Updates import accordingly

# Before: two separate implementations + filename-based dispatch
if 'activity' in filename.lower():
    images, svgs, pngs = plot_activity_graphs(df, divs, [metric], genotypes, colors)
elif 'networks' in filename.lower():
    images, svgs, pngs = plot_bar_with_p_values(df, divs, [metric], genotypes, colors)
else:
    raise TypeError("No file of name activity or network found")

# After: unified call regardless of file type
images, svgs, pngs = plot_metrics_graphs(df, divs, [metric], genotypes, colors)