fix(a11y): improve alt text in features and kanvas visuals

[Manishnemade12]

Summary

This PR improves accessibility (WCAG-focused image semantics) by fixing missing/generic/empty alt usage in high-impact Components and Kanvas sections.

Closes : #7614

What changed

• Updated instructional/meaningful images to use descriptive alt text.
• Marked decorative images with alt="" and aria-hidden="true".
• Replaced generic alt text ("image") with context-aware text.

Files updated

• src/components/Features/index.js
• src/sections/Kanvas/Kanvas-collaborate/kanvas-collaborate-banner.js
• src/components/Academy/Features-Section/AcademyFeaturesMobileSwiper.js
• src/components/Academy/Features-Section/AcademyFeaturesCarousel.js
• src/sections/Kanvas/Kanvas-design/Kanvas_Mobile_swiper/KanvasMobileSwiper.js
• src/sections/Kanvas/Kanvas-design/kanvas-design-features-carousel.js
• src/sections/Kanvas/FeaturesSection/Collaborate/CollaboratorFeatures_diagram.js

Impact

• Improves screen-reader accessibility for instructional visuals.
• Reduces ambiguous image announcements from generic alt values.
• Preserves decorative behavior where images are non-informational.

Validation

• Editor diagnostics checked for all changed files: no errors reported.
• No tests were run.

[Manishnemade12]

@rishiraj38 Can you please review this pr