feat: UI/UX overhaul — CSS cleanup, accessibility, error handling, inline style extraction

Phase 0 — CSS-only fixes:
- Fix --font-mono to use real monospace stack (JetBrains Mono, Fira Code, etc.)
- Replace hardcoded hex colors with CSS variables across 16+ files
- Merge global-nav.css (507 lines) into layout.css, delete original
- Reduce !important in responsive.css from 71 to 8 via .app-shell specificity
- Standardize breakpoints to 480/768/1024/1280px

Phase 1 — Loading states & SSE connection feedback:
- Add centralized SSEManager (sse-manager.js) with exponential backoff
- Add SSE status indicator dot in nav bar
- Add withLoadingButton() + .btn-loading CSS spinner
- Add mode section crossfade transitions

Phase 2 — Accessibility:
- Add aria-labels to icon-only buttons across mode partials
- Add for/id associations to 42 form labels in 5 mode partials
- Add aria-live on toast stack, enableListKeyNav() utility

Phase 3 — Destructive action guards & list overflow:
- Add confirmAction() styled modal, replace all 25 native confirm() calls
- Add toast cap at 5 simultaneous toasts
- Add list overflow indicator CSS

Phase 4 — Inline style extraction:
- Refactor switchMode() in app.js and index.html to use classList.toggle()
- Add CSS toggle rules for all switchMode-controlled elements
- Remove inline style="display:none" from 7+ HTML elements
- Add utility classes (.hidden, .d-flex, .d-grid, etc.)

Phase 5 — Mobile UX polish:
- pre/code overflow handling already in place
- Touch target sizing via --touch-min variable

Phase 6 — Error handling consistency:
- Add reportActionableError() to user-facing catch blocks in 5 mode JS files
- 28 error toast additions alongside existing console.error calls

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

static/js/modes/wefax.js

@@ -242,6 +242,7 @@ var WeFax = (function () {
             .catch(function (err) {
                 setStatus('Stopped');
                 console.error('WeFax stop error:', err);
+                reportActionableError('Stop WeFax', err);
             });
     }
 
@@ -626,9 +627,15 @@ var WeFax = (function () {
         gallery.innerHTML = html;
     }
 
-    function deleteImage(filename) {
+    async function deleteImage(filename) {
         if (!filename) return;
-        if (!confirm('Delete this image?')) return;
+        const confirmed = await AppFeedback.confirmAction({
+            title: 'Delete Image',
+            message: 'Delete this image? This cannot be undone.',
+            confirmLabel: 'Delete',
+            confirmClass: 'btn-danger'
+        });
+        if (!confirmed) return;
         fetch('/wefax/images/' + encodeURIComponent(filename), { method: 'DELETE' })
             .then(function (r) { return r.json(); })
             .then(function (data) {
@@ -641,12 +648,18 @@ var WeFax = (function () {
             })
             .catch(function (err) {
                 console.error('WeFax delete error:', err);
-                setStatus('Delete failed: ' + err.message);
+                reportActionableError('Delete Image', err);
             });
     }
 
-    function deleteAllImages() {
-        if (!confirm('Delete all WeFax images?')) return;
+    async function deleteAllImages() {
+        const confirmed = await AppFeedback.confirmAction({
+            title: 'Delete All Images',
+            message: 'Delete all WeFax images? This cannot be undone.',
+            confirmLabel: 'Delete All',
+            confirmClass: 'btn-danger'
+        });
+        if (!confirmed) return;
         fetch('/wefax/images', { method: 'DELETE' })
             .then(function (r) { return r.json(); })
             .then(function (data) {
@@ -654,7 +667,10 @@ var WeFax = (function () {
                     loadImages();
                 }
             })
-            .catch(function (err) { console.error('WeFax delete all error:', err); });
+            .catch(function (err) {
+                console.error('WeFax delete all error:', err);
+                reportActionableError('Delete All Images', err);
+            });
     }
 
     var currentModalUrl = null;
@@ -1107,6 +1123,7 @@ var WeFax = (function () {
             })
             .catch(function (err) {
                 console.error('WeFax scheduler disable error:', err);
+                reportActionableError('Disable Scheduler', err);
             });
     }