Share Mark Complete modal as partial view; hide install button after PWA install

- Extract _CompleteJobModal.cshtml partial; Details.cshtml uses PartialAsync
- Job board COMPLETED drop fetches partial via AJAX and shows modal in-place
- Add GET Jobs/CompleteJobModal action to load job data for the board modal
- install-app.js: persist installed state in localStorage; clears automatically when browser re-fires beforeinstallprompt after uninstall

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/wwwroot/js/install-app.js

@@ -1,12 +1,15 @@
 // Browser-aware install UX for supported PWAs.
 // Shows a real install button only when the browser exposes the install prompt,
 // and falls back to platform-specific instructions for iOS Safari.
+// After install the button is hidden; if the user later uninstalls, the browser
+// re-fires beforeinstallprompt which clears the flag and shows the button again.
 (function () {
     'use strict';
 
     const installBtn = document.getElementById('installAppBtn');
     if (!installBtn) return;
 
+    const INSTALLED_KEY = 'pclAppInstalled';
     const ua = navigator.userAgent || '';
     const isIos = /iphone|ipad|ipod/i.test(ua);
     const isIosSafari = isIos && /safari/i.test(ua) && !/crios|fxios|edgios/i.test(ua);
@@ -51,6 +54,13 @@
             return;
         }
 
+        // Hide if already installed and browser hasn't re-offered the prompt
+        // (flag is cleared automatically when beforeinstallprompt fires again after uninstall)
+        if (localStorage.getItem(INSTALLED_KEY) === '1') {
+            hideInstallButton();
+            return;
+        }
+
         if (deferredPrompt) {
             showInstallButton('prompt', 'Install App', 'bi-download');
             return;
@@ -64,14 +74,18 @@
         hideInstallButton();
     }
 
+    // Browser fires this when the app becomes installable (including after an uninstall).
+    // Clearing the flag here ensures the button reappears if the user previously uninstalled.
     window.addEventListener('beforeinstallprompt', function (event) {
         event.preventDefault();
         deferredPrompt = event;
+        localStorage.removeItem(INSTALLED_KEY);
         refreshInstallUi();
     });
 
     window.addEventListener('appinstalled', function () {
         deferredPrompt = null;
+        localStorage.setItem(INSTALLED_KEY, '1');
         hideInstallButton();
     });
 
@@ -84,7 +98,10 @@
             deferredPrompt.prompt();
 
             try {
-                await deferredPrompt.userChoice;
+                const choice = await deferredPrompt.userChoice;
+                if (choice.outcome === 'accepted') {
+                    localStorage.setItem(INSTALLED_KEY, '1');
+                }
             } catch {
                 // Ignore prompt result errors; the browser owns the final install flow.
             }