keep EasyMDE on desktop/Android, fall back to plain textarea only on iOS

Dropping EasyMDE entirely (previous commit) fixed the Korean IME jamo split
but also removed the live markdown syntax highlighting everywhere, even on
platforms that never had the bug. Only iOS WebKit breaks CJK IME composition
under CodeMirror, so journal-editor.js now detects iOS (including the
desktop-UA-masquerading iPad, via MacIntel + multi-touch) and only skips
EasyMDE there, falling back to a native <textarea>. Everywhere else keeps
the full EasyMDE/CodeMirror editing experience as before.

window.JournalEditor now dispatches to the right engine per textarea
(checking t._easymde) so the toolbar buttons and the category-template
autofill in journal.html work unchanged regardless of which engine backs a
given textarea. Restores the easymde vendor files, base.html includes, and
service worker precache entries removed in the previous commit (cache
bumped to v8).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/templates/journal.html

@@ -134,7 +134,7 @@
       if (this.content === this.lastAutoFilled) {
         this.content = tmpl;
         this.lastAutoFilled = tmpl;
-        this.$nextTick(() => { this.$refs.contentField.dispatchEvent(new Event('input')); });
+        this.$nextTick(() => { JournalEditor.setValue(this.$refs.contentField, tmpl); });
       }
     },
     init() { this.onCategoryChange(this.$refs.categorySelect.value); },