fix: browser back gesture closes modal instead of navigating (#36)

* fix: browser back gesture closes modal instead of navigating

- Push history state when opening medication detail modal
- Handle popstate event to close modal on browser back
- Replace direct setSelectedMed(null) with closeMedDetail() helper
- Improves mobile UX: swiping back closes modal instead of leaving page

* feat: add back-swipe support for all modals

- Add history.pushState/popstate handling for all modal types
- Profile, ShareDialog, EditModal, RefillModal, ImageLightbox,
  ScheduleLightbox, UserFilter now all support browser back button
- Mobile users can now swipe back to close any modal instead of
  navigating away from the app
- ESC key also triggers proper history-based close for all modals
- Fix duplicate openShareDialog function
- Fix recursive call bug in openUserFilter

* fix: prevent past days count from wrapping to new line

- Add flex-wrap: nowrap to .past-days-toggle
- Add white-space: nowrap and flex-shrink: 0 to .past-days-count
- Ensures (7 Tage), (14 Tage) etc. stays on same line as label

* fix: improve schedule row layout for mobile screens

- Stack schedule label and value vertically on small screens (<400px)
- Add word-break for long text values
- Prevents 'Einnahmeprüfung' and '15 Min. vor geplanter Zeit' from overlapping

* feat: add back-swipe support for image lightbox on share page

- Add history.pushState/popstate handling for lightbox in SharedSchedule
- Mobile users can now swipe back to close image instead of navigating away

frontend/src/styles.css

@@ -677,6 +677,7 @@ textarea.auto-resize {
 .past-days-toggle {
   display: flex;
   align-items: center;
+  flex-wrap: nowrap;
   gap: 0.5rem;
   padding: 0.75rem 1rem;
   background: var(--bg-tertiary);
@@ -702,6 +703,7 @@ textarea.auto-resize {
 .past-days-icon {
   font-size: 0.7rem;
   opacity: 0.6;
+  flex-shrink: 0;
 }
 .past-days-label {
   font-weight: 500;
@@ -709,6 +711,8 @@ textarea.auto-resize {
 .past-days-count {
   opacity: 0.6;
   font-size: 0.85rem;
+  white-space: nowrap;
+  flex-shrink: 0;
 }
 .past-days-warning {
   margin-left: auto;
@@ -2055,7 +2059,8 @@ textarea.auto-resize {
 .schedule-row {
   display: flex;
   justify-content: space-between;
-  align-items: center;
+  align-items: flex-start;
+  gap: 0.5rem;
   padding: 0.35rem 0;
   font-size: 0.85rem;
 }
@@ -2068,11 +2073,27 @@ textarea.auto-resize {
 
 .schedule-label {
   color: var(--text-secondary);
+  flex-shrink: 0;
+  min-width: 0;
 }
 
 .schedule-value {
   color: var(--text-primary);
   font-weight: 500;
+  text-align: right;
+  word-break: break-word;
+}
+
+/* Mobile: stack schedule rows vertically when text is long */
+@media (max-width: 400px) {
+  .schedule-row {
+    flex-direction: column;
+    align-items: flex-start;
+    gap: 0.25rem;
+  }
+  .schedule-value {
+    text-align: left;
+  }
 }
 
 /* Legacy support for old channel-btn (can remove later) */