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/shared/SettingsView.tsx

@@ -183,7 +183,7 @@ function ExportSection() {
     setErrorMsg(null);
     try {
       const filePath = await save({
-        defaultPath: `wrystr-export-${new Date().toISOString().slice(0, 10)}.json`,
+        defaultPath: `vega-export-${new Date().toISOString().slice(0, 10)}.json`,
         filters: [{ name: "JSON", extensions: ["json"] }],
       });
       if (!filePath) {