Add free-text day notes with an always-visible notes log

A new 📝 Note quick-action logs a free-text note (with a date, optional
photo, and any text), defaulting to the day you're viewing. Notes are a
distinct "note" event type, so they edit, sync and delete like any other
event, and a new Notes section lists them newest-first across every day —
independent of the day picker — so records like vaccinations stay visible
whatever day you're looking at.

src/index.html

@@ -113,6 +113,7 @@
           <button class="action pee" data-type="pee">💧 Pee</button>
           <button class="action poo" data-type="poo">💩 Poo</button>
           <button class="action weight" data-type="weight">⚖️ Weigh-in</button>
+          <button class="action note" data-type="note">📝 Note</button>
         </div>
       </section>
 
@@ -261,6 +262,12 @@
         <p id="weight-empty" class="empty">No weigh-ins logged yet.</p>
       </section>
 
+      <section class="notes-log" data-panel="notes">
+        <h2>Notes</h2>
+        <ul id="notes-list" class="event-list"></ul>
+        <p id="notes-empty" class="empty">No notes yet. Use the 📝 Note button to jot down things like vaccinations or vet visits — they'll be listed here across every day.</p>
+      </section>
+
       <section class="history" data-panel="history">
         <h2>History</h2>
         <ul id="event-list" class="event-list"></ul>