chore(site): sync release data, add download filters, and fix Lighthouse performance/accessibility issues

[harsha-vardhan-burra]

Description

Changes Made

• Replaced the hand-maintained changelog/release arrays with a data-driven pipeline (scripts/sync-releases.mjs + raw-releases.json/raw-changelog.md → normalized-releases.json) so release notes sync directly from GitHub.
• Added Stable / Beta / Alpha filters on the Downloads page via classifyRelease().
• Marked legacy v1.x/v2.x releases as deprecated: isDeprecatedRelease(), a "Deprecated" tag + warning banner on changelog entries, and matching treatment on download cards.
• Corrected copy that overstated security/privacy guarantees (e.g. "encrypted", "true sovereignty", "vault") to match what the app actually does, and fixed broken/incorrect links (Contributing guide, Issues, License).
• Added a Community Manager entry to the contributors list and a "Design by" credit link in the footer.
• Fixed Lighthouse-flagged performance and accessibility issues on /downloads:
  • Converted the store badge and logo to correctly-sized WebP (with PNG fallback) instead of serving oversized PNGs, and added explicit width/height.
  • Deferred GithubStarDialog and PowerShortcuts with next/dynamic to cut unused JS on first load.
  • Added a font fallback stack for font-display: swap to reduce the heading layout shift on web-font load.
  • Removed aria-labels that no longer matched their visible button text.
  • Adjusted --text-dim contrast to meet the 4.5:1 WCAG threshold.
  • Reserved layout space (min-height, contain: layout) around the store-badge section and removed the transform from the page-enter animation to reduce CLS.
  • Enabled productionBrowserSourceMaps for debuggable production bundles.
• Added a Playwright E2E suite (smoke + functional specs covering homepage, downloads, changelog, footer, community, mobile, and theming) with a CI workflow and TESTING.md.

Breaking Changes / Compatibility

• Changelog and release content is now generated from src/data/raw-releases.json / raw-changelog.md via scripts/sync-releases.mjs instead of being edited directly in src/lib/changelog.ts — future release notes should go through that pipeline instead.
• No changes to exported hook/component APIs; isDeprecatedRelease is additive to src/lib/github.ts.

Notes

• This branch bundles several previously-separate concerns (content fixes, release-data pipeline, download filters, deprecation UI, community/footer credits, Lighthouse fixes, and E2E tests) into one PR — worth flagging in case reviewers would rather split it up.
• A few early commits' content edits (Hero.tsx, FeatureGrid.tsx, CommunityContent.tsx, ContactContent.tsx) show no net diff against main, since equivalent fixes already landed via fix(site): refine homepage and community interactions #48/feat(site): implement automated release sync and visual refinements #49 — worth a quick rebase check before merging to avoid stale/duplicate commits in history.
• The performance commit directly resolves the Lighthouse findings from the /downloads page audit (oversized images, CLS sources, mismatched accessible names, missing source maps).