Add bulk set field (Storage Location, Brand) to dashboard toolbar

Select batteries, choose field and value from toolbar, hit Apply.
Storage Location dropdown populated from existing locations.

app.py

@@ -28,7 +28,13 @@ def create_app(config_object="config"):
     @app.route("/")
     def dashboard():
         batteries = db.query(Battery).order_by(Battery.label).all()
-        return render_template("dashboard.html", batteries=batteries)
+        storage_locations = [
+            r[0] for r in db.query(Battery.storage_location)
+            .filter(Battery.storage_location.isnot(None))
+            .distinct().order_by(Battery.storage_location).all()
+        ]
+        return render_template("dashboard.html", batteries=batteries,
+                               storage_locations=storage_locations)
 
     # ------------------------------------------------------------------ #
     # Battery — add
@@ -278,6 +284,21 @@ 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 == "set_field":
+            field_name = request.form.get("field_name", "").strip()
+            field_value = request.form.get("field_value", "").strip() or None
+            allowed = {"brand", "storage_location"}
+            if field_name not in allowed:
+                flash("Invalid field.", "error")
+                return redirect(url_for("dashboard"))
+            if field_name == "brand" and not field_value:
+                flash("Brand name is required.", "error")
+                return redirect(url_for("dashboard"))
+            for b in batteries:
+                setattr(b, field_name, field_value)
+            db.commit()
+            label = field_name.replace("_", " ").title()
+            flash(f"Set {label} on {n} batter{'y' if n == 1 else 'ies'}.", "success")
         else:
             flash("Unknown action.", "error")