Add brand autocomplete dropdown to battery add and device install forms

Uses HTML datalist populated from distinct brands in the battery table.
Removed autocomplete="off" which suppresses datalist in Chrome/Chromium.

app.py

@@ -46,8 +46,10 @@ def create_app(config_object="config"):
 
             if not brand:
                 flash("Brand is required.", "error")
+                brands = [r[0] for r in db.query(Battery.brand).distinct().order_by(Battery.brand).all()]
                 return render_template("battery_add.html",
-                                       form_brand="", form_count=1, form_notes=notes or ""), 400
+                                       form_brand="", form_count=1, form_notes=notes or "",
+                                       brands=brands), 400
 
             existing = db.query(func.count(Battery.id)).filter_by(brand=brand).scalar()
             for i in range(count):
@@ -57,7 +59,8 @@ def create_app(config_object="config"):
             flash(f"Added {count} {brand} batter{'y' if count == 1 else 'ies'}.", "success")
             return redirect(url_for("dashboard"))
 
-        return render_template("battery_add.html", form_count=1)
+        brands = [r[0] for r in db.query(Battery.brand).distinct().order_by(Battery.brand).all()]
+        return render_template("battery_add.html", form_count=1, brands=brands)
 
     # ------------------------------------------------------------------ #
     # Battery — detail
@@ -290,7 +293,8 @@ def create_app(config_object="config"):
         device = db.get(Device, device_id)
         if device is None:
             abort(404)
-        return render_template("device_detail.html", device=device)
+        brands = [r[0] for r in db.query(Battery.brand).distinct().order_by(Battery.brand).all()]
+        return render_template("device_detail.html", device=device, brands=brands)
 
     # ------------------------------------------------------------------ #
     # Devices — install batteries