fix: image lightbox overlay hidden not working — display:flex overrode hidden class

- Removed display:flex from inline style so the hidden class can apply display:none
- All image modals were visible and stacked on top of the page content
- This also blocked event creation (the transparent overlay covered the form)

templates/event_expenses.html

@@ -57,7 +57,7 @@
                         </div>
                     </div>
                     {{if .ImagePath}}
-                    <div id="img-{{.ID}}" class="hidden" style="position: fixed; inset: 0; background: rgba(0,0,0,0.85); z-index: 999; display: flex; align-items: center; justify-content: center; cursor: pointer; padding: 1rem;"
+                    <div id="img-{{.ID}}" class="hidden" style="position: fixed; inset: 0; background: rgba(0,0,0,0.85); z-index: 999; align-items: center; justify-content: center; cursor: pointer; padding: 1rem;"
                          onclick="this.classList.add('hidden')">
                         <img src="/storage/{{.ImagePath}}" alt="Receipt" style="max-width: 100%; max-height: 100%; object-fit: contain; border-radius: 0.5rem;">
                     </div>

templates/expense_list.html

@@ -45,7 +45,7 @@
                 </button>
             </div>
             {{if .ImagePath}}
-            <div id="img-{{.ID}}" class="hidden" style="position: fixed; inset: 0; background: rgba(0,0,0,0.85); z-index: 999; display: flex; align-items: center; justify-content: center; cursor: pointer; padding: 1rem;"
+            <div id="img-{{.ID}}" class="hidden" style="position: fixed; inset: 0; background: rgba(0,0,0,0.85); z-index: 999; align-items: center; justify-content: center; cursor: pointer; padding: 1rem;"
                  onclick="this.classList.add('hidden')">
                 <img src="/storage/{{.ImagePath}}" alt="Receipt" style="max-width: 100%; max-height: 100%; object-fit: contain; border-radius: 0.5rem;">
             </div>