refactor(ui): replace Text with Label/Widget component system

Replace the old `Text` class with a new component-based UI system consisting of `Widget` and `Label` classes. Key changes:

- Remove `Text` class and its GPU upload logic; introduce `Label` as a `Widget` subclass with dirty-flag vertex update.
- Add `UIVertexData` struct to manage per-label vertex buffer/array and memory.
- Refactor `DebugCollector` to store labels in a `Widget` tree, removing hash-based lookup.
- Simplify `Font::vertices()` signature by removing position/scale parameters; scaling is now applied in the renderer’s model matrix.
- Update `Renderer` with `render_label()` and move UI rendering to a `render_ui()` that renders the widget tree.
- Add new source files `label.cpp`, `widget.cpp`, `ui_vertex_data.cpp` and update CMakeLists.

src/ui/label.cpp

@@ -0,0 +1,58 @@
+#include "Cubed/ui/label.hpp"
+
+#include "Cubed/render/renderer.hpp"
+#include "Cubed/tools/font.hpp"
+namespace Cubed {
+Label::Label(const std::string& id) : Widget(id) {}
+
+Label& Label::set_text(std::string_view text) {
+    m_text.text = text;
+    m_dirty = true;
+    return *this;
+}
+
+Label& Label::set_position(const glm::vec2& pos) {
+    return set_position(pos.x, pos.y);
+}
+
+Label& Label::set_position(float x, float y) {
+    m_pos.x = x;
+    m_pos.y = y;
+    return *this;
+}
+
+Label& Label::set_scale(float scale) {
+    m_scale = scale;
+    return *this;
+}
+
+Label& Label::set_color(Color color) {
+    m_text.color = color;
+    return *this;
+}
+
+void Label::update(float dt) { on_update(dt); }
+
+void Label::on_update(float dt) {
+    (void)dt;
+    if (m_dirty) {
+        update_vertices();
+        m_dirty = false;
+    }
+}
+
+void Label::render(Renderer& renderer) { on_render(renderer); }
+
+void Label::on_render(Renderer& renderer) { renderer.render_lable(*this); }
+
+void Label::update_vertices() {
+    m_data.m_vertices = Font::vertices(m_text.text);
+    m_data.update_sum();
+    m_data.upload();
+}
+
+const UIVertexData& Label::data() const { return m_data; }
+const glm::vec2& Label::pos() const { return m_pos; }
+const TextStyle& Label::text_style() const { return m_text; }
+float Label::scale() const { return m_scale; }
+} // namespace Cubed