Add bulk install-in-device from dashboard and unretire action

- Dashboard bulk toolbar: select batteries, pick a device, click 'Install
  in device'; confirms before moving already-installed batteries; enforces
  slot capacity and warns on brand mix
- Battery detail: 'Unretire Battery' button replaces 'Retire Battery' when
  battery is retired, restoring it to available status
- Tests: 3 new bulk-install-device tests (capacity block, move, success);
  42 total passing

app.py

@@ -225,6 +225,23 @@ def create_app(config_object="config"):
         flash(f"{battery.label} has been retired.", "success")
         return redirect(url_for("dashboard"))
 
+    # ------------------------------------------------------------------ #
+    # Battery — unretire
+    # ------------------------------------------------------------------ #
+
+    @app.route("/battery/<int:battery_id>/unretire", methods=["POST"])
+    def battery_unretire(battery_id):
+        battery = db.get(Battery, battery_id)
+        if battery is None:
+            abort(404)
+        if not battery.is_retired():
+            flash(f"{battery.label} is not retired.", "error")
+            return redirect(url_for("battery_detail", battery_id=battery_id))
+        battery.status = "available"
+        db.commit()
+        flash(f"{battery.label} is now available again.", "success")
+        return redirect(url_for("battery_detail", battery_id=battery_id))
+
     # ------------------------------------------------------------------ #
     # Battery — delete
     # ------------------------------------------------------------------ #
@@ -285,6 +302,55 @@ def create_app(config_object="config"):
                 b.brand = new_brand
             db.commit()
             flash(f"Updated brand to '{new_brand}' for {n} batter{'y' if n == 1 else 'ies'}.", "success")
+        elif action == "install_device":
+            device_id = request.form.get("device_id", type=int)
+            if not device_id:
+                flash("Please select a device.", "error")
+                return redirect(url_for("dashboard"))
+            device = db.get(Device, device_id)
+            if device is None:
+                flash("Device not found.", "error")
+                return redirect(url_for("dashboard"))
+
+            already_here = [b for b in batteries if b.device_id == device.id]
+            retired_sel  = [b for b in batteries if b.is_retired()]
+            to_process   = [b for b in batteries
+                            if b.device_id != device.id and not b.is_retired()]
+
+            if not to_process:
+                flash("No eligible batteries to install.", "error")
+                return redirect(url_for("dashboard"))
+
+            free_slots = device.battery_slots - device.installed_count()
+            if len(to_process) > free_slots:
+                flash(
+                    f"{device.name} only has {free_slots} free slot(s), "
+                    f"but {len(to_process)} need installing.",
+                    "error",
+                )
+                return redirect(url_for("dashboard"))
+
+            existing_brands = device.installed_brands()
+            new_brands = set(b.brand for b in to_process)
+            if existing_brands and (new_brands - existing_brands):
+                flash(f"Warning: mixing brands in {device.name}.", "warning")
+
+            for b in to_process:
+                b.status = "installed"
+                b.device_id = device.id
+            db.commit()
+
+            msg = (f"Installed {len(to_process)} "
+                   f"batter{'y' if len(to_process) == 1 else 'ies'} in {device.name}.")
+            notes = []
+            if already_here:
+                notes.append(f"{len(already_here)} already there")
+            if retired_sel:
+                notes.append(f"{len(retired_sel)} retired skipped")
+            if notes:
+                msg += f" ({', '.join(notes)}.)"
+            flash(msg, "success")
+
         elif action == "set_field":
             field_name = request.form.get("field_name", "").strip()
             field_value = request.form.get("field_value", "").strip() or None

templates/battery_detail.html

@@ -185,6 +185,10 @@
       <form method="post" action="{{ url_for('battery_retire', battery_id=battery.id) }}">
         <button class="btn btn-secondary" type="submit">Retire Battery</button>
       </form>
+    {% else %}
+      <form method="post" action="{{ url_for('battery_unretire', battery_id=battery.id) }}">
+        <button class="btn btn-secondary" type="submit">Unretire Battery</button>
+      </form>
     {% endif %}
 
     <a class="btn btn-danger" href="{{ url_for('battery_delete', battery_id=battery.id) }}">Delete Battery</a>

templates/dashboard.html

@@ -113,6 +113,17 @@
         </span>
         <button class="btn btn-sm btn-primary" name="action" value="set_field" type="submit">Apply</button>
       </span>
+      <span style="display:flex;gap:0.35rem;align-items:center;">
+        <select id="bulk-device-select" name="device_id"
+                style="padding:0.25rem 0.5rem;font-size:0.85rem;border:1px solid #cbd5e1;border-radius:4px;">
+          <option value="">— select device —</option>
+          {% for d in devices %}
+          <option value="{{ d.id }}">{{ d.name }} ({{ d.installed_count() }}/{{ d.battery_slots }})</option>
+          {% endfor %}
+        </select>
+        <button class="btn btn-sm btn-primary" name="action" value="install_device" type="submit"
+                onclick="return confirmInstallDevice()">Install in device</button>
+      </span>
     </div>
 
     <div class="table-wrap">
@@ -260,6 +271,23 @@ function applyFilters() {
   updateToolbar();
 }
 
+function confirmInstallDevice() {
+  var deviceSel = document.getElementById('bulk-device-select');
+  if (!deviceSel.value) { deviceSel.focus(); return false; }
+  var movers = Array.prototype.filter.call(
+    document.querySelectorAll('.row-cb:checked'),
+    function(cb) { return cb.closest('tr').dataset.status === 'installed'; }
+  );
+  if (movers.length > 0) {
+    var n = movers.length;
+    return confirm(
+      n + ' selected batter' + (n === 1 ? 'y is' : 'ies are') +
+      ' already installed elsewhere. Unassign and move to the selected device?'
+    );
+  }
+  return true;
+}
+
 function quickAssign(action, batteryId) {
   var sel = document.getElementById('qas-' + batteryId);
   if (!sel.value) { sel.focus(); return; }

tests/test_acceptance.py

@@ -294,6 +294,45 @@ def test_device_install_over_capacity(client):
     assert b"slot" in resp.data.lower()
 
 
+def test_bulk_install_device(client):
+    """Select multiple available batteries and install them into a device."""
+    client.post("/device/add", data={"name": "Box", "battery_slots": "3"})
+    client.post("/battery/add", data={"brand": "Eneloop", "count": "2"})
+    resp = client.post("/battery/bulk-action",
+                       data={"battery_ids": ["1", "2"], "action": "install_device",
+                             "device_id": "1"},
+                       follow_redirects=True)
+    assert resp.status_code == 200
+    assert b"Installed 2" in resp.data
+
+
+def test_bulk_install_device_over_capacity(client):
+    """Bulk install is blocked when device lacks free slots."""
+    client.post("/device/add", data={"name": "Box", "battery_slots": "1"})
+    client.post("/battery/add", data={"brand": "Eneloop", "count": "2"})
+    resp = client.post("/battery/bulk-action",
+                       data={"battery_ids": ["1", "2"], "action": "install_device",
+                             "device_id": "1"},
+                       follow_redirects=True)
+    assert resp.status_code == 200
+    assert b"slot" in resp.data.lower()
+
+
+def test_bulk_install_device_moves_installed_battery(client):
+    """Bulk install moves a battery already installed in another device."""
+    client.post("/device/add", data={"name": "Box A", "battery_slots": "2"})
+    client.post("/device/add", data={"name": "Box B", "battery_slots": "2"})
+    client.post("/battery/add", data={"brand": "Eneloop", "count": "1"})
+    client.post("/battery/1/assign", data={"device_id": "1"})
+    resp = client.post("/battery/bulk-action",
+                       data={"battery_ids": ["1"], "action": "install_device",
+                             "device_id": "2"},
+                       follow_redirects=True)
+    assert resp.status_code == 200
+    assert b"Installed 1" in resp.data
+    assert b"Box B" in client.get("/battery/1").data
+
+
 # ------------------------------------------------------------------ #
 # Dashboard — quick-assign
 # ------------------------------------------------------------------ #