feat: add IndieHunt footer badge

[andrewzolotukhin]

Original request

Add an IndieHunt badge to the site using the supplied light and dark theme SVG snippets, follow the $pr-workflow, and do not create a blog post.

What changed

• Added a themed IndieHunt badge to the public landing-page footer.
• Linked the badge to https://indiehunt.io/project/xpenser in a new tab with rel="noopener".
• Used the supplied 265×58 light and dark SVG assets with the light image shown in light mode and the dark image shown in dark mode.
• Added component coverage for the destination, external-link attributes, image sources, dimensions, and theme classes.
• Added Playwright coverage for light/dark visibility on the public index.

Reasoning

The implementation follows the existing footer badge convention: both theme images live inside one accessible, keyboard-focusable link so users see a single badge and a single focus target. The supplied URLs, alt text, dimensions, and link attributes are preserved exactly.

Blog post

Skipped. This is a small footer badge addition, and the original request explicitly asked for no blog post.

Screenshots / Preview

Preview: https://xpenser-pr-085.cleverbrush.com

Light theme asset	Dark theme asset

Manual preview QA at 1440×1000 confirmed:

• The IndieHunt badge fits the existing footer badge grid without overflow or overlap.
• Light mode shows only the light SVG; dark mode shows only the dark SVG.
• Both variants render at 265×58.
• The accessible link targets https://indiehunt.io/project/xpenser with _blank and noopener.
• Browser runtime reported no page errors.

Validation

• npm run lint — 359 files checked
• npm run typecheck — 11 tasks passed
• npm test — 95 files and 520 tests passed
• Focused apps/web/components/landing-page.test.tsx — 1 test passed
• Lint and test GitHub check
• Deploy PR environment GitHub check
• Playwright e2e GitHub check
• Preview QA in light and dark themes
• SigNoz checked for service.name = xpenser-web-pr-85; no matching log, trace, or http.server.duration.count resources were available, so telemetry is explicitly recorded as unavailable for this static footer preview rather than reported as a pass.

Checklist

• I kept the change focused.
• I updated docs or tests where needed.
• I checked for secrets, local env files, and generated build output.
• API changes keep contracts, endpoint metadata, and handlers aligned (not applicable; no API changes).