refactor: address remaining accessibility, contrast, type safety, dead code, and UX enhancements

[TarunyaProgrammer]

Summary

This issue tracks the resolution of all remaining lower-priority and style-related findings (🟠/🟡/💡) from the application audit. Resolving these concerns ensures fully semantic HTML structure and ARIA keyboard support, improves color contrast to pass WCAG AA standards, removes redundant/dead code and duplicate functions, hardens type safety across Angular/NestJS, and cleans up several UX inconsistencies.

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1. Accessibility (a11y) Improvements (Frontend)

• Semantic Anchors in Sidebar Menu: Refactor <div role="link"> in navbar.component.html to use standard <a> elements with [routerLink] so right-click actions and browser link affordances work correctly.
• Semantic Nav Landmarks: Change the desktop main sidebar div.navbar to a <nav aria-label="Main Navigation"> landmark to eliminate duplicate landmark confusion.
• Remove Redundant Bottom Nav Attributes: Clean up mobile bottom nav items to remove redundant role="link" on <a> tags and use standard [routerLink] routing.
• Overlay Div Space Key: Add (keydown.space) alongside the existing enter key listener on the side menu overlay in navbar.component.html for standard button keyboard semantics.
• Hero Search Trigger Role: Add role="button" and aria-label="Search projects" to the search trigger div on the homepage.component.html.
• Aria-Hidden Unicode Arrows: Wrap the → character inside links on the homepage with <span aria-hidden="true">→</span> to prevent screen readers from announcing it.

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2. Contrast & Visual Enhancements (Frontend)

• Darken --text-muted in Light Mode: Change --text-muted in styles.scss from #94A3B8 to #6B7280 to pass WCAG AA contrast (4.5:1).
• Darken --text-secondary in Light Mode: Darken --text-secondary from #5B6470 to #4B5563 to ensure it passes WCAG AA on the off-white #F7F7F2 background.
• Correct Dark Mode --profile-github-bg: The --success color (#00C16A) used as the GitHub profile badge background fails contrast checks with white text in dark mode. We will replace it with a darker green (#059669) in dark mode.
• Fix SVG Accent Stroke Contrast: Change the hand-drawn SVG arrow stroke in homepage.component.html from var(--accent-lime) to a readable color in light mode.
• Fix Dark Mode --card-dark-2 Value: --card-dark-2 is currently set to #dcdcdc (a light gray) inside the dark theme ruleset. We will correct this to a dark slate background (#1E293B).

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3. Redundant & Dead Code Cleanups

• Delete Unused CommmonUtilService: Remove commmon-util.service.ts completely (it only hosts unused global mutable states).
• Clean Up Unused Injections in ProjectsComponent: Remove unused http and toastr injections from projects.component.ts.
• Remove Redundant RouterModule Import: Remove RouterModule from standalone standalone imports in app.component.ts (as RouterOutlet is already imported).
• Remove Unused errorInterceptor Alias: Remove the dead alias re-export in error.interceptor.ts.
• Dynamic Year Determination: Replace hardcoded currentYear = 2026 defaults with dynamic new Date().getFullYear() across the navbar and dashboards.
• Consolidate extractCookie Helper: Move the three duplicate private implementations of extractCookie from backend files into the centralized cookie-helper.ts utility.

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4. Architectural & Type Safety Hardening

• Clean Up Admin Component HTTP Subscriptions: Implement takeUntilDestroyed(this.destroyRef) on admin component API subscriptions to prevent leaks.
• Enforce Strict Types on Admin Dashboard Data: Define proper TypeScript interfaces for dashboardData, audit logs, and ideaForm instead of relying on any.
• Type DTO Parameters in GSoC Service: Type the inputs for createIdea and updateIdea in gsoc.service.ts.
• Type GitHub API Repositories: Declare and use a concrete GithubRepo type for repository arrays inside the backend project.service.ts.

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5. UX & Logic Enhancements

• Show Spinner During Admin Auth Checks: Show a loading state in admin.component.ts during session verification instead of briefly flashing the login form.
• Fix Unused Card Component for Empty State: Replace the dummy <app-projects-card> empty state on the projects page with a clean message container.
• Switch Projects Search to Two-Way Binding: Refactor projects page search input to use [(ngModel)]="searchTerm" for seamless synchronization.
• Refactor toggleMode Double Negation: Clean up the double negation assignment to isSunVisible inside admin components.
• Hide Pagination on Single Pages: Add @if (totalPages > 1) checks to pagination controls on projects and contributors views.
• Add Login Input Password Hint: Add autocomplete="current-password" to the admin login form password input.
• Add Missing Head Metadata: Add type="application/manifest+json" and og:image tags to index.html.
• Backend Cache Size Limit: Add a capacity ceiling and scheduled cleanup sweep to the server CacheService to prevent unbounded memory growth.