Point desktop downloads at 0.3.0; release v5.5.3

The Download block still offered desktop 0.1.0 — the build from before in-app
updates, the voice-note fixes and the verification hardening. Windows, macOS and
Linux now link to 0.3.0.

The version was repeated across three URLs in two different forms: two resolved
through /releases/latest/download/ and one pinned a tag. That is how they drifted
out of date, so it is now one constant.

The tag stays pinned on purpose. Release filenames carry the version, so a
/latest/ link breaks the moment a newer release exists, while a pinned tag keeps
serving a working installer — the safer way to fail if the constant is ever left
behind.

src/app.jsx

@@ -3533,7 +3533,7 @@ import {
                             }
                         }
 
-                        handleMessage(' SecureBit.chat Enhanced Security Edition v5.5.2 - ECDH + DTLS + SAS initialized. Ready to establish a secure connection with ECDH key exchange, DTLS fingerprint verification, and SAS authentication to prevent MITM attacks.', 'system');
+                        handleMessage(' SecureBit.chat Enhanced Security Edition v5.5.3 - ECDH + DTLS + SAS initialized. Ready to establish a secure connection with ECDH key exchange, DTLS fingerprint verification, and SAS authentication to prevent MITM attacks.', 'system');
 
                         // Setup file transfer callbacks (id-bound to THIS session's manager).
                         manager.setFileTransferCallbacks(

src/components/ui/DownloadApps.jsx

@@ -1,9 +1,19 @@
+// Desktop release these links point at. Bump this one constant when a new
+// desktop version ships — the version used to be repeated in three URLs in two
+// different forms, which is how they ended up stuck on 0.1.0.
+//
+// The tag is pinned rather than using /releases/latest/download/: the filenames
+// carry the version, so a `latest` link 404s the moment a newer release exists,
+// whereas a pinned tag keeps serving a working (if older) installer.
+const DESKTOP_VERSION = '0.3.0';
+const DESKTOP_RELEASE = `https://github.com/SecureBitChat/securebit-desktop/releases/download/v${DESKTOP_VERSION}`;
+
 const DownloadApps = () => {
     const apps = [
         { id: 'web', name: 'Web App', subtitle: 'Browser Version', icon: 'fas fa-globe', platform: 'Web', isActive: true, url: 'https://securebit.chat/', color: 'green' },
-        { id: 'windows', name: 'Windows', subtitle: 'Desktop App', icon: 'fab fa-windows', platform: 'Desktop', isActive: true, url: 'https://github.com/SecureBitChat/securebit-desktop/releases/latest/download/SecureBit.Chat_0.1.0_x64-setup.exe', color: 'blue' },
-        { id: 'macos', name: 'macOS', subtitle: 'Desktop App', icon: 'fab fa-safari', platform: 'Desktop', isActive: true, url: 'https://github.com/SecureBitChat/securebit-desktop/releases/download/v0.1.0/SecureBit.Chat_0.1.0_x64.dmg', color: 'gray' },
-        { id: 'linux', name: 'Linux', subtitle: 'Desktop App', icon: 'fab fa-linux', platform: 'Desktop', isActive: true, url: 'https://github.com/SecureBitChat/securebit-desktop/releases/latest/download/SecureBit.Chat_0.1.0_amd64.AppImage', color: 'orange' },
+        { id: 'windows', name: 'Windows', subtitle: 'Desktop App', icon: 'fab fa-windows', platform: 'Desktop', isActive: true, url: `${DESKTOP_RELEASE}/SecureBit.Chat_${DESKTOP_VERSION}_x64-setup.exe`, color: 'blue' },
+        { id: 'macos', name: 'macOS', subtitle: 'Desktop App', icon: 'fab fa-safari', platform: 'Desktop', isActive: true, url: `${DESKTOP_RELEASE}/SecureBit.Chat_${DESKTOP_VERSION}_x64.dmg`, color: 'gray' },
+        { id: 'linux', name: 'Linux', subtitle: 'Desktop App', icon: 'fab fa-linux', platform: 'Desktop', isActive: true, url: `${DESKTOP_RELEASE}/SecureBit.Chat_${DESKTOP_VERSION}_amd64.AppImage`, color: 'orange' },
         { id: 'ios', name: 'iOS', subtitle: 'iPhone & iPad', icon: 'fab fa-apple', platform: 'Mobile', isActive: false, url: 'https://apps.apple.com/app/securebit-chat/', color: 'white' },
         { id: 'android', name: 'Android', subtitle: 'Google Play', icon: 'fab fa-android', platform: 'Mobile', isActive: false, url: 'https://play.google.com/store/apps/details?id=com.securebit.chat', color: 'green' },
         { id: 'chrome', name: 'Chrome', subtitle: 'Browser Extension', icon: 'fab fa-chrome', platform: 'Browser', isActive: false, url: '#', color: 'yellow' },

src/components/ui/Header.jsx

@@ -559,7 +559,7 @@ const EnhancedMinimalHeader = ({
                     React.createElement('div', { key: 'txt', style: { lineHeight: 1.2, minWidth: 0 } }, [
                         React.createElement('div', { key: 'r1', style: { display: 'flex', alignItems: 'baseline', gap: '7px' } }, [
                             React.createElement('span', { key: 'n', style: { fontSize: '16px', fontWeight: 800, letterSpacing: '-0.3px', color: '#e8e8eb' } }, 'SecureBit'),
-                            React.createElement('span', { key: 'v', style: { fontFamily: MONO, fontSize: '10px', fontWeight: 500, color: '#56565e' } }, 'v5.5.2')
+                            React.createElement('span', { key: 'v', style: { fontFamily: MONO, fontSize: '10px', fontWeight: 500, color: '#56565e' } }, 'v5.5.3')
                         ]),
                         React.createElement('div', { key: 'r2', className: 'hidden sm:block', style: { fontSize: '11px', color: '#6b6b73', fontWeight: 500 } }, 'End-to-end encrypted')
                     ])