deploy: add Linux install script download

apps/api/src/server.ts

@@ -75,6 +75,10 @@ app.get('/downloads/fieldlens-print-linux-x64.deb', (_req, res) => {
   redirectDesktopDownload(res, 'fieldlens-print-linux-x64.deb')
 })
 
+app.get('/downloads/install.sh', (_req, res) => {
+  redirectDesktopDownload(res, 'install.sh')
+})
+
 // Backward-compatible aliases used by the first downloads page.
 app.get('/downloads/fieldlens-print/windows-x64', (_req, res) => {
   redirectDesktopDownload(res, 'fieldlens-print-windows-x64-setup.exe')

apps/web/src/DesktopDownloads.tsx

@@ -13,6 +13,12 @@ const downloads = [
     detail: 'x64 · Debian / Ubuntu .deb package',
     icon: Terminal,
   },
+  {
+    href: '/downloads/install.sh',
+    label: 'Linux install script',
+    detail: 'x64 · verifies SHA-256 · installs the .deb',
+    icon: Terminal,
+  },
 ]
 
 export function DesktopDownloadsLink({ onOpen }: { onOpen: () => void }) {
@@ -70,8 +76,14 @@ export function DesktopDownloadsPage({ onBack }: { onBack: () => void }) {
             ))}
           </div>
 
+          <div className="downloads-command">
+            <span>Linux quick install</span>
+            <code>curl -fsSL https://fieldlens.arrowstack.dev/downloads/install.sh | sh</code>
+          </div>
+
           <div className="downloads-notes">
             <p><strong>Windows:</strong> installs for the current user, so the app itself does not require administrator elevation.</p>
+            <p><strong>Linux script:</strong> supports x86_64/amd64 Debian/Ubuntu-style systems and verifies the package checksum before installation.</p>
             <p><strong>Printer setup:</strong> changing a managed Windows printer queue or port can still require IT/admin permission.</p>
           </div>
         </section>

apps/web/src/host.css

@@ -167,7 +167,7 @@
 }
 .desktop-download-grid {
   display: grid;
-  grid-template-columns: repeat(2, minmax(0, 1fr));
+  grid-template-columns: repeat(3, minmax(0, 1fr));
   gap: 12px;
   padding: 18px 20px;
 }
@@ -255,3 +255,31 @@
   cursor: pointer;
   font: inherit;
 }
+
+
+.downloads-command {
+  display: grid;
+  gap: 7px;
+  padding: 0 20px 18px;
+}
+.downloads-command span {
+  color: #75807b;
+  font-size: 9px;
+  font-weight: 800;
+  text-transform: uppercase;
+  letter-spacing: .08em;
+}
+.downloads-command code {
+  display: block;
+  overflow-x: auto;
+  padding: 11px 12px;
+  border: 1px solid #dfe3dc;
+  border-radius: 10px;
+  background: #17211f;
+  color: #f6f5ed;
+  font-size: 10px;
+  white-space: nowrap;
+}
+@media (max-width: 980px) and (min-width: 761px) {
+  .desktop-download-grid { grid-template-columns: 1fr; }
+}