test: Implement frontend component tests for core UI

[Uche44]

Summary

This PR adds unit and integration tests for all major frontend components in the application. Before this, only one component test existed. Adding these tests prevents visual or functional regression bugs when changes are made to these files.

Specifically, I added tests for:

• StreamViewer: Verified connection status and feed updates.
• StreamFeed: Verified empty state message and rendering a list of events.
• ConnectionStatus: Verified the correct color badge is rendered for all 4 states (connecting, connected, disconnected, error).
• StreamTagChips: Verified tag names and delete button click actions.
• TagCombobox: Verified opening popover, search filtering, tag loading/errors, and adding or creating tags.
• StreamTagEditor: Verified tag attaching/detaching operations, optimistic updates, and automatic rollback on API errors.
• EmbedSnippet: Verified iframe code generation, copy to clipboard function (async & fallback), and developer-environment security checks.
• AdminDashboard: Verified initial loading skeleton, success stats rendering, auto-refresh intervals, and showing stale data on fetch failures.

Related issue

Closes: #200

Type of change

• feat
• fix
• docs
• chore
• test
• ci

Testing performed

We ran the test runner in the app directory. All 44 tests in the 10 test suites successfully pass in under 9 seconds.
npm run test --prefix app

[Xhristin3]

Hey @Uche44 \u2014 excellent test coverage across StreamViewer, dashboard, tags, and embed components. The optimistic-update rollback in stream-tag-editor is a particularly nice touch. 44/44 in under 9s is a great signal. Closes #200 and merged. Thanks for the work! \ud83e\uddea