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/components/sidebar/Sidebar.tsx

@@ -53,7 +53,7 @@ export function Sidebar() {
           /* Expanded: brand on left, collapse chevron on right */
           <>
             <div className="flex flex-col">
-              <span className="text-sm font-bold tracking-widest text-text select-none">WRYSTR</span>
+              <span className="text-sm font-bold tracking-widest text-text select-none">VEGA</span>
               <span className="text-text-dim text-[9px] font-mono opacity-50">v{pkg.version}</span>
             </div>
             <button