feat: add z posish

also osc shit

frontend/src/components/Slider.svelte

@@ -0,0 +1,59 @@
+<script lang="ts">
+  import type { TrackerData } from "$lib/utils/types";
+
+  type Props = {
+    selected: number;
+    trackers: TrackerData[];
+    ws: WebSocket | null;
+    width: number;
+    height: number;
+  };
+
+  let {
+    selected = $bindable(),
+    trackers = $bindable(),
+    ws,
+    width = $bindable(),
+    height = $bindable(),
+  }: Props = $props();
+
+  const onchange = () => {
+    const x_send = trackers[selected].x / width;
+    const y_send = trackers[selected].y / height;
+    ws?.send(
+      JSON.stringify({
+        id: trackers[selected].id,
+        x: x_send,
+        y: y_send,
+        z: trackers[selected].z,
+      }),
+    );
+  };
+
+  let z_viz = $derived((trackers[selected].z * 2).toFixed(2))
+</script>
+
+<div>
+  <label for="z">Z</label>
+  <input
+    type="range"
+    id="z"
+    min="0"
+    max="1"
+    step="0.01"
+    oninput="{onchange}"
+    bind:value={trackers[selected].z}
+  />
+  <output for="z">{z_viz} m</output>
+</div>
+
+<style>
+  input {
+    writing-mode: vertical-lr;
+    direction: rtl;
+    appearance: slider-vertical;
+    width: 26px;
+    height: 50%;
+    vertical-align: bottom;
+  }
+</style>