[Frontend][Testing] implemented frontend testing with full coverage

[vegeshop]

• Implemented testing for App.tsx, Ingredient.tsx with full coverage.
• Implemented testing for user/fridge actions
• Introduced testing for placeholder components(10+)
• Make it fully covered without CreateRecipe
• Fixed some unique child key issue.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

100.0% Coverage
0.0% Duplication