Add bulk Log Charged action to dashboard toolbar

Select multiple batteries, pick a date, and optionally increment charge
cycles for all of them in one shot. Reuses the existing bulk-action form
and POST /battery/bulk-action route; no new routes or migrations needed.

app.py

@@ -470,6 +470,24 @@ def create_app(config_object="config"):
             db.commit()
             label = field_name.replace("_", " ").title()
             flash(f"Set {label} on {n} batter{'y' if n == 1 else 'ies'}.", "success")
+        elif action == "log_charged":
+            date_val = request.form.get("charged_date", "").strip()
+            if not date_val:
+                flash("Date is required.", "error")
+                return redirect(url_for("dashboard"))
+            increment = 1 if request.form.get("increment_cycles") else 0
+            for b in batteries:
+                db.add(ChargeLog(battery_id=b.id, charged_date=date_val,
+                                 increment_cycles=increment, notes=None))
+                if increment:
+                    b.charge_cycles = (b.charge_cycles or 0) + 1
+            db.commit()
+            flash(
+                f"Logged charge date {date_val} for "
+                f"{n} batter{'y' if n == 1 else 'ies'}"
+                + (" (+cycles)." if increment else "."),
+                "success",
+            )
         else:
             flash("Unknown action.", "error")