Routing: Drag & drop reordering and single add button for routing waypoints

[dopenguin]

Description

Rework the waypoint input handling so that waypoints can be reordered via drag & drop and new waypoints are added only through a single button placed below the input list instead of being inserted at arbitrary positions. Since drag & drop makes ordering explicit, positional insertion via per-row add buttons is no longer needed.

Current behavior

• Each waypoint row in RoutingInput.ce.vue has its own 'add' button that inserts a new empty input at that specific index (routeStore.setRoute(index)).
• There is no way to reorder existing waypoints.
• The order is only controllable by inserting at a specific position.
• Each row also has a 'remove' button, with a minimum of two waypoints enforced (route.length === 2).

Expected behavior

• Users can reorder existing waypoint inputs (the route array in store.ts) via drag & drop with an accessible, keyboard-operable alternative (e.g. move up / move down).
• On reorder, the route array order updates so the route request reflects the new sequence.
• The per-row 'add' button is removed. A single 'add waypoint' button appears below the input list in RoutingWrapper.ce.vue and appends a new empty waypoint at the end.
• The existing 'max two fillable inputs' guard (addWaypointButtonDisabled) is preserved on the new single add button.
• The per-row remove button and the minimum-of-two-waypoints constraint remain unchanged.

Affected areas

File	What needs to change
src/plugins/routing/components/RoutingInput.ce.vue	Remove the add button, add drag handle / reorder controls.
src/plugins/routing/components/RoutingWrapper.ce.vue	Render the single add button below the v-for input list.
src/plugins/routing/store.ts	Adjust setRoute (or add dedicated append + reorder actions) to support append-at-end and reordering of the route array. Consider resetting currentlyFocusedInput on reorder.

Out of scope

Changes to the routing request/response logic beyond honoring the new waypoint order.