[Enhancement] Add a combined "Total" metric line to the [HISTORICAL_DATA] chart for clearer activity tracking

[Yashaswini-K-P]

Description

1. The Core Idea & Current Limitation

The [HISTORICAL_DATA] section on the user profile currently tracks cumulative solved questions broken down by individual difficulties (Easy, Medium, Hard) using shell-script style view toggles (./weekly.sh, ./monthly.sh, ./overall.sh).

Because the graph displays separate lines for each difficulty without a primary combined total, it is difficult to quickly evaluate at a glance whether a user had actual activity or a flat plateau on a given day without mentally adding up the individual counts.

2. Proposed Solution

• Introduce a combined Total Solved dataset line into the Chart.js configuration alongside or above the existing difficulty breakdown lines.
• Compute the total dynamically (either via backend sync updates or frontend summation of Easy + Medium + Hard for each timeline entry).
• Style the Total line with a distinct, prominent color (e.g., bright blue/cyan) so student activity levels and plateau periods are instantly noticeable.

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[jagdish-15]

I think this is a nice improvement and I'd be happy to have it implemented.

Before working on this, could you also open a separate issue (or expand this one if you prefer) to align the graph colours with the rest of the application? The main leaderboard already uses colours that exactly match LeetCode's difficulty colours, whereas the charts on the user profile and the comparison modal bar graphs currently use a slightly different palette.

The idea would be to first update both the user profile graphs and the comparison modal bar graphs to use the same colour scheme as the leaderboard, and then implement the new Total Solved line on top of that. This will keep the visual theme consistent across the application.

[TanCodeX]

@jagdish-15 Please assign me this under gssoc.

[aaniya22]

pls assign this to me under gssoc

[Yashaswini-K-P]

@jagdish created a separate issue for colour scheme