Chore: Resolve Deprecated Packages (Recharts v3, ESLint v9, Next-PWA)

[ArshVermaGit]

Description

This PR eliminates the massive wall of deprecation warnings (inflight, rollup-plugin-terser, recharts, eslint) that were clogging up the npm install logs and introducing future technical debt.

Resolved Issue

Resolves #1539

Fixes:

• 📈 Recharts Migration: Upgraded from ^2.12.7 to ^3.8.1. This removes legacy React 17 dependencies (like defaultProps) and improves SSR compatibility.
• ⚙️ Next PWA Fork: The original next-pwa package is dead. Replaced it with the community-maintained @ducanh2912/next-pwa drop-in replacement, which purges the deprecated rollup-plugin-terser sub-dependency.
• 🧹 ESLint Flat Config: Upgraded ESLint to ^9.0.0 and migrated the legacy .eslintrc.json to the modern Flat Config (eslint.config.mjs). Also cleaned up several unused eslint-disable comments across the codebase.
• 🚀 SSR Optimization: Removed { ssr: false } from our dynamic chart imports in DashboardPage, allowing Next.js 15 to properly render the skeleton loaders on the server.

Breaking Changes / Follow-ups Needed

The major version bumps to Next.js 15 and Recharts v3 introduced a few strict TypeScript errors that currently fail the npm run build step (e.g., req.ip was removed from NextRequest, and Recharts Tooltip generic types have changed). These will need to be patched before this can be deployed.

How to Verify

1. Pull down this branch.
2. Run npm install and verify the output is perfectly clean (0 deprecation warnings).
3. Run npm run lint and verify there are no ESLint errors.
4. Run npm run test to verify the unit test suite still passes.

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[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

Difficulty (pick one):

• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

Quality (optional):

• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

Validation (required to score):

• gssoc:approved — counts for points
• gssoc:invalid / gssoc:spam / gssoc:ai-slop — does not score

Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus

[ArshVermaGit]

Hi @Priyanshu-byte-coder ! Issue #1539 has been resolved. Please review the PR and merge it under GSSoC. Thanks!

[Priyanshu-byte-coder]

This PR now has merge conflicts with main due to recent merges. Please rebase onto the latest main branch and resolve conflicts before we can merge.

[ArshVermaGit]

This PR now has merge conflicts with main due to recent merges. Please rebase onto the latest main branch and resolve conflicts before we can merge.

Done Please review!