feat: add shuffle button for theme presets

[opinder8699]

Description

Adds a Shuffle Theme button to the customize page so users can quickly preview random preset themes without manually cycling through the dropdown.

Fixes #136

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix, refactoring, docs)

##Changes Made
-[x]Added a Shuffle icon button using lucide-react
-[x]Implemented handleRandomTheme for random preset selection
-[x]Excluded the auto theme from shuffle behavior
-[x]Prevented immediate repetition of the currently active theme
-[x]Added hover, scale, and active click animations

Visual Preview

Added a shuffle button beside the theme selector for quick random theme discovery.

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have started the repo.
• I have made sure that i have only one commit to merge in this PR.

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