feat(ui): add reusable copy-to-clipboard component with success anima…

[Honey-pg]

Introduce shared clipboard utility, hook, and CopyToClipboardButton with checkmark feedback and a 2.5s Copied state. Migrate existing copy actions across profile sharing, settings, goals, streaks, and career tools.

Summary

Adds a reusable copy-to-clipboard system with consistent visual feedback (Copy → checkmark animation + temporary "Copied!" state). Replaces 10+ ad-hoc clipboard implementations across the app so profile links, share actions, and content copies behave the same way.

Closes #1937

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that changes existing behavior)
• 📝 Documentation update
• ♻️ Refactor / code cleanup (no functional change)
• ⚡ Performance improvement
• 🔒 Security fix
• 🧪 Tests only

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What Changed

• Added src/lib/copy-to-clipboard.ts — shared clipboard API with execCommand fallback
• Added src/hooks/useCopyToClipboard.ts — copied state (2.5s reset), optional toast, per-id tracking, onSuccess callback
• Added src/components/CopyToClipboardButton.tsx — reusable button with Copy/Check icons, aria-live, and optional showToast
• Refactored src/components/CopyLinkButton.tsx — thin wrapper preserving existing url prop API
• Migrated copy actions in: ShareProfileButton, dashboard settings page, WeeklySummaryCard, StreakTracker, GoalTracker, BadgeSection, ExportPanel, ResumePreview, RoastHypeWidget
• Added test/copy-to-clipboard.test.ts — utility + hook tests

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How to Test

1. Run unit tests: npm test test/copy-to-clipboard.test.ts
2. Open /dashboard → click Share Profile in the header — confirm checkmark + "Copied" for ~2.5s (toast optional)
3. Visit Settings → public profile URL Copy, and a public profile /u/[username] Copy link — same feedback pattern
4. Test other migrated surfaces: goal share link, streak copy button, AI summary copy, roast/hype output copy, resume export copy

Expected result: Every copy action shows a checkmark animation and temporary success state. Optional toasts appear only where showToast is enabled (e.g. profile share, settings, streak stats). No duplicate or inconsistent "Copied" UI.

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Screenshots / Recordings

Recommended: short screen recording of Share Profile → Copied state, and one icon-only copy (e.g. streak or AI summary).

Before	After
Mixed copy feedback (text-only, icons, toasts, inconsistent timing)	Unified Copy → Check animation + 2.5s "Copied!" state

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Checklist

• Linked the related issue above
• Self-reviewed my own diff
• No unnecessary console.log, debug code, or commented-out blocks
• npm run lint passes locally
• No TypeScript errors (npm run type-check) — pre-existing failure: missing @google/generative-ai in unrelated file
• Added or updated tests where applicable
• Updated documentation / comments if behavior changed

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Accessibility (UI changes only)

• Keyboard navigation works correctly — uses standard Button component
• Color contrast meets WCAG AA standard — success state uses var(--success)
• ARIA labels / roles added where needed — aria-live="polite", dynamic aria-label on copy/copied
• Tested on mobile / responsive layout

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Additional Context

• CopyLinkButton API is unchanged for existing consumers (ShareProfileSection, public profile page).
• Toast notifications are optional (showToast prop, default false); enabled where they existed before (profile share, settings, streak copy).
• useCopyToClipboard supports per-item tracking via copy(text, id) for list UIs like goal share links.

[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