fix: trigger species search on button click, not on input change

Avoids burning Perenual API quota on every keystroke.

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

plants/templates/plants/species_search.html

@@ -4,17 +4,23 @@
 <h5 class="mb-3">Add a plant</h5>
 <p class="text-muted small">Search for the species to auto-fill care info, or skip to enter details manually.</p>
 
-<input
-    type="search"
-    class="form-control mb-2"
-    placeholder="🔍 Search species, e.g. 'climbing rose'"
-    hx-get="{% url 'species_search' %}"
-    hx-trigger="input changed delay:400ms"
-    hx-target="#species-results"
-    hx-swap="innerHTML"
-    name="q"
-    autocomplete="off"
->
+<div class="input-group mb-2">
+    <input
+        type="search"
+        class="form-control"
+        placeholder="e.g. 'climbing rose'"
+        name="q"
+        id="species-q"
+        autocomplete="off"
+    >
+    <button
+        class="btn btn-success"
+        hx-get="{% url 'species_search' %}"
+        hx-include="#species-q"
+        hx-target="#species-results"
+        hx-swap="innerHTML"
+    >Search</button>
+</div>
 
 <div id="species-results" class="list-group mb-3"></div>