Add matching quiz type, more theme colors, animal icon picker, and fix color persistence

- Fix theme not saving across sessions: /api/state was missing `theme` in SELECT
- Add 4 new color themes: red, teal, yellow, indigo (student + admin)
- Add animal icon picker (32 animals) with PATCH /api/students/:id/emoji endpoint
- Add Matching item type: word bank (A, B, C… alphabetical) + clue blanks, auto-graded
- Matching submit button stays disabled until all blanks are filled

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

public/admin.html

@@ -129,6 +129,7 @@
               <option value="quiz">❓ Quiz</option>
               <option value="spelling_practice">✏️ Spelling Practice</option>
               <option value="spelling_test">⭐ Spelling Test</option>
+              <option value="matching">🔤 Matching</option>
               <option value="flashcards">🗂️ Flashcards</option>
             </select>
           </label>
@@ -234,6 +235,12 @@
             <button type="button" id="ie-add-question" class="secondary">+ Add question</button>
           </div>
 
+          <div id="ie-field-matching" class="ie-field">
+            <p class="hint" style="margin-bottom:.5rem">Enter word-clue pairs. Words are shown as A, B, C… (alphabetical order) in the word bank.</p>
+            <div id="ie-pairs"></div>
+            <button type="button" id="ie-add-pair" class="secondary">+ Add pair</button>
+          </div>
+
           <div id="ie-field-spelling" class="ie-field">
             <label>Word list <select id="ie-list"></select></label>
           </div>