Rename Wrystr to Vega

Named after Jurij Vega (1754-1802), Slovenian mathematician who made
knowledge accessible through his logarithm tables. Rebrand before
OpenSats application (April 1).

- Product name, window title, identifiers, binary name all renamed
- Cargo package: wrystr -> vega, wrystr_lib -> vega_lib
- PKGBUILD: wrystr -> vega (new AUR package name)
- Release workflow: artifact names, release text updated
- README: new tagline referencing Jurij Vega
- DB migration: auto-renames wrystr.db -> vega.db on first launch
- Keyring service name kept as "wrystr" for backward compatibility
- localStorage keys kept as wrystr_* to preserve existing user data

Pending manual steps:
- Rename GitHub repo hoornet/wrystr -> hoornet/vega
- Create new AUR package vega-git, orphan wrystr-git
- Update local .desktop launcher

src/App.tsx

@@ -35,7 +35,7 @@ function UpdateBanner() {
   return (
     <div className="flex items-center justify-between px-4 py-2 bg-accent/10 border-b border-accent/30 text-[12px] shrink-0">
       <span className="text-text">
-        Wrystr {version} is available.{" "}
+        Vega {version} is available.{" "}
         {error && <span className="text-danger ml-1">{error}</span>}
       </span>
       <div className="flex items-center gap-3">