Add Smooth Animated Entry Experience for All Users

[Dushyantcoder07]

Summary [required]

This PR adds a smooth, lightweight entry animation sequence to the homepage so the initial load feels more polished and engaging for all users, without changing core functionality or layout behavior. It introduces subtle fade-in and slide-up motion with staggered timing across hero content and key landing sections, keeps the experience responsive on mobile and desktop, and respects accessibility/performance best practices by avoiding heavy effects and preserving a clean, non-distracting DevPath visual flow.

Related Issue [required]

Closes #317

Type of Change [required]

• Bug fix — resolves a broken behaviour
• Feature — adds new functionality
• Data — adds new projects to data/projects.json
• Documentation — updates docs, README, or code comments only
• [x ] Style — CSS or visual changes only, no logic change
• Refactor — restructures code without changing behaviour
• Test — adds or updates tests

What Was Changed [required]

| File | Change made |

index.html | Add the entry animation trigger on page load

style.css | Add fade/slide-up keyframes and staggered animation styles

script.js | Only needed later if any JavaScript-based animation hook is added

How to Test This PR [required]

1. Checkout the branch: git checkout Entry-effect
2. Install dependencies: py -m pip install -r requirements.txt
3. Run the app: py app.py
4. Open http://127.0.0.1:5000 and verify the homepage entry animations appear smoothly
5. Run tests: py tests/test_basic.py

Expected test output:

30 passed, 0 failed out of 30 tests

Test Results [required]

All tests completed successfully with no failures.(30 passed, 0 failed out of 30 tests)

Screenshots (if UI change)

Screenshot is not possible to take because of very less time effect. And all things are remains same so it cant make any difference.

Self-Review Checklist [required]

• [x ] I have read CONTRIBUTING.md and followed all guidelines
• [ x] My branch name follows the convention: feat/, fix/, docs/, data/, style/, test/
• [ x] I have run python tests/test_basic.py and all 27 tests pass
• [ x] I have run flake8 . locally and there are no errors
• [ x] I have not introduced any print() or console.log() debug statements
• [ x] Every new function I wrote has a docstring
• [ x] I have not modified files outside the scope of the linked issue
• [ x] If I changed the UI, I tested it at 375px (mobile) and 1280px (desktop)
• [ x] If I added a project to the dataset, it has all required JSON fields

Notes for Reviewer

This PR adds a smooth entry animation experience on the homepage for all users using lightweight CSS-based fade/slide transitions with staggered timing.
No business logic or backend behavior was changed; updates are limited to UI presentation and were verified locally (app run + basic tests passing).

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[Dushyantcoder07]

Please review the changes @komalharshita .