Add device_type field, mobile-friendly improvements, and device filtering

- Device model: add device_type column (String 50, nullable)
- Device add/edit: type select with presets + custom entry
- Device detail: show type in info card; new Edit Device form
- Device list: Type column + client-side filter bar (type + text search)
- Mobile: card-style responsive tables on dashboard and device list,
  form-grid-2col collapse, larger tap targets, stacked form-actions,
  column picker viewport fix, filter bar full-width controls
- Assign page: larger radio touch targets (min-height 44px)
- 3 new acceptance tests for device_type (45 total)

templates/device_add.html

@@ -18,6 +18,27 @@
              value="{{ form_slots|default(1) }}" min="1" required>
     </div>
 
+    <div class="form-group">
+      <label>Type</label>
+      {% set _preset_types = ['Remote Control','Game Controller','Flashlight','Lock','Sensor','Toy','Clock','Smoke Detector'] %}
+      {% set _cur_type = form_device_type|default('') %}
+      <select id="device-type-select" onchange="metaSelectChanged(this,'device_type')">
+        <option value="">— none —</option>
+        {% for opt in _preset_types %}
+        <option value="{{ opt }}" {% if _cur_type == opt %}selected{% endif %}>{{ opt }}</option>
+        {% endfor %}
+        {% for opt in device_types|default([]) %}
+          {% if opt not in _preset_types %}
+        <option value="{{ opt }}" {% if _cur_type == opt %}selected{% endif %}>{{ opt }}</option>
+          {% endif %}
+        {% endfor %}
+        <option value="__new__" {% if _cur_type and _cur_type not in _preset_types and _cur_type not in device_types|default([]) %}selected{% endif %}>Other…</option>
+      </select>
+      <input type="text" id="device_type" name="device_type" value="{{ _cur_type }}"
+             placeholder="Enter device type"
+             style="display:{% if _cur_type and _cur_type not in _preset_types %}''{% else %}none{% endif %};margin-top:0.4rem;">
+    </div>
+
     <div class="form-group">
       <label for="notes">Notes</label>
       <textarea id="notes" name="notes" placeholder="Optional notes…">{{ form_notes|default('') }}</textarea>
@@ -29,4 +50,18 @@
     </div>
   </form>
 </div>
+
+<script>
+function metaSelectChanged(sel, inputId) {
+  var input = document.getElementById(inputId);
+  if (sel.value === '__new__') {
+    input.style.display = '';
+    input.value = '';
+    input.focus();
+  } else {
+    input.style.display = 'none';
+    input.value = sel.value;
+  }
+}
+</script>
 {% endblock %}