feat: password change + split account/household settings UI

- New /change-password route: validates current password,
  enforces min 4 chars, requires confirmation match
- update_password() helper in models.py
- Dashboard UI split into two collapsible sections:
  👤 Account Settings (password, ntfy, delete account)
  🏠 Household Settings (admin only: public link, timezone,
     delete household)
- 14 new i18n keys with fr/de translations
- Restored accidentally dropped 'Delete My Account' key

meals.py

@@ -12,7 +12,7 @@ from flask import (
     flash,
 )
 
-from werkzeug.security import check_password_hash
+from werkzeug.security import check_password_hash, generate_password_hash
 
 from models import (
     get_dashboard_data,
@@ -33,6 +33,7 @@ from models import (
     get_household_by_public_token,
     generate_public_token,
     set_public_enabled,
+    update_password,
 )
 from i18n import t
 from ntfy import send_test_notification, send_meal_reminder
@@ -191,6 +192,33 @@ def delete_account():
     return redirect(url_for("auth.login"))
 
 
+@meals_bp.route("/change-password", methods=["POST"])
+@login_required
+def change_password():
+    """Change the logged-in user's password."""
+    current = request.form.get("current_password", "")
+    new = request.form.get("new_password", "")
+    confirm = request.form.get("confirm_password", "")
+
+    user = get_user_by_id(session["user_id"])
+
+    if not check_password_hash(user["password_hash"], current):
+        flash(t("Current password is incorrect."), "error")
+        return redirect(url_for("meals.dashboard"))
+
+    if len(new) < 4:
+        flash(t("New password must be at least 4 characters."), "error")
+        return redirect(url_for("meals.dashboard"))
+
+    if new != confirm:
+        flash(t("New passwords do not match."), "error")
+        return redirect(url_for("meals.dashboard"))
+
+    update_password(session["user_id"], generate_password_hash(new))
+    flash(t("Password changed successfully."), "success")
+    return redirect(url_for("meals.dashboard"))
+
+
 @meals_bp.route("/admin/remove-user/<int:user_id>", methods=["POST"])
 @login_required
 def admin_remove_user(user_id):