Update Cozystack logo and favicons to the new brand mark (#551)

## Summary

Refreshes the site's Cozystack branding to the new logo (icon +
`COZYSTACK` wordmark):

- **`assets/icons/logo.svg`** — replaced with the new horizontal
wordmark (white, for the dark navigation bar).
- **`static/favicons/*`** — the full favicon set regenerated from the
new icon glyph.

## Details

- Favicons use the new icon on a `#1a1a1a` square, matching the site's
existing `theme_color` / `TileColor`.
- All favicon file names and pixel dimensions are unchanged
(`favicon.ico` keeps 16/32/48, mstiles keep their existing sizes, etc.),
so `favicons.html`, `site.webmanifest` and `browserconfig.xml` need no
edits.
- Logo and favicon SVGs were optimized with https://autocrop.cncf.io.
- The AEnix logo (`content/en/img/logo.png`) and component logos are
intentionally left untouched.

## Test plan

- [ ] Run the site locally and confirm the new logo renders in the
navbar.
- [ ] Check the browser tab favicon and the PWA/installed icons.

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## Summary by CodeRabbit

* **Style**
* Increased navigation bar logo height for improved visual presentation.

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Author: kvaps

assets/icons/logo.svg

@@ -37,7 +37,7 @@ nav.navbar {
     svg {
       display: inline-block;
       margin: 0 10px 0 -6px;
-      height: 30px;
+      height: 36px;
       @include media-breakpoint-up(lg) {
         margin: 0 10px;
       }