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/Controllers/JobsController.cs

@@ -2643,6 +2643,22 @@ public class JobsController : Controller
 
     #region Job Completion
 
+    /// <summary>
+    /// Returns the Mark Complete modal partial view populated with full job data.
+    /// Called via AJAX from the Job Board when a card is dragged to the Completed column.
+    /// </summary>
+    [HttpGet]
+    public async Task<IActionResult> CompleteJobModal(int id)
+    {
+        var job = await _unitOfWork.Jobs.LoadForDetailsAsync(id);
+        if (job == null) return NotFound();
+        var currentUser = await _userManager.GetUserAsync(User);
+        if (currentUser != null)
+            await PopulateEmailNotificationDefaultsAsync(currentUser.CompanyId);
+        var dto = _mapper.Map<JobDto>(job);
+        return PartialView("_CompleteJobModal", dto);
+    }
+
     /// <summary>
     /// Marks a job as completed, recording actual time spent and final price adjustments.
     /// Updates the CompletedDate, ActualTimeSpentHours, and FinalPrice fields, transitions to