docs(readme): serve footer social badges + star-history from snapshots (#261)

Pairs with **wickra-lib/.github#32**. The README footer (GitHub stars / forks / issues) hot-linked `img.shields.io` directly, so it showed shields' transient **"unable to select next github token from pool"** error live; the star-history chart hot-linked `star-history.com` and **froze** behind GitHub's Camo image cache (the embedded `<img>` is proxied + cached, while the linked page renders fresh).

All four now point at the committed snapshots in the `.github` repo (`raw.githubusercontent.com/wickra-lib/.github/main/profile/badges/{stars,forks,issues,star-history}.svg`), refreshed hourly by the new `refresh-social.yml` — so a broken upstream never reaches the page and the last good SVG is always served. The `<a>` links and the visual style are unchanged.

## Merge order
Merge **.github#32 first** (it creates the snapshot SVGs), then this one — otherwise the footer would briefly point at missing raw URLs.

Not merging yet — for review.

README.md

@@ -419,13 +419,13 @@ The library is provided **as is**, without warranty of any kind; see
 
 <p align="center">
   <a href="https://github.com/wickra-lib/wickra/stargazers">
-    <img alt="GitHub stars" src="https://img.shields.io/github/stars/wickra-lib/wickra?style=for-the-badge&logo=github&logoColor=white&color=ffd866">
+    <img alt="GitHub stars" src="https://raw.githubusercontent.com/wickra-lib/.github/main/profile/badges/stars.svg">
   </a>
   <a href="https://github.com/wickra-lib/wickra/network/members">
-    <img alt="GitHub forks" src="https://img.shields.io/github/forks/wickra-lib/wickra?style=for-the-badge&logo=github&logoColor=white&color=78dce8">
+    <img alt="GitHub forks" src="https://raw.githubusercontent.com/wickra-lib/.github/main/profile/badges/forks.svg">
   </a>
   <a href="https://github.com/wickra-lib/wickra/issues">
-    <img alt="GitHub issues" src="https://img.shields.io/github/issues/wickra-lib/wickra?style=for-the-badge&logo=github&logoColor=white&color=ff6188">
+    <img alt="GitHub issues" src="https://raw.githubusercontent.com/wickra-lib/.github/main/profile/badges/issues.svg">
   </a>
 </p>
 
@@ -436,6 +436,6 @@ The library is provided **as is**, without warranty of any kind; see
 <p align="center">
   <a href="https://star-history.com/#wickra-lib/wickra&Date">
     <img alt="Wickra star history" width="640"
-         src="https://api.star-history.com/svg?repos=wickra-lib/wickra&type=Date&theme=dark">
+         src="https://raw.githubusercontent.com/wickra-lib/.github/main/profile/badges/star-history.svg">
   </a>
 </p>