feat(aigc): add user agreement page and update consent dialog

Add new AIGC user agreement page with scrollable markdown rendering, loading and retry states.
Register the new route in pages.json.
Restructure AigcConsentDialog's content into styled sections, and update its rule click handler to navigate directly to the new agreement page.

src/pages-aigc/agreement/styles/index.scss

@@ -0,0 +1,54 @@
+.aigc-agreement-page {
+  width: 100%;
+  height: 100vh;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+  background: #ffffff;
+}
+
+.aigc-agreement-scroll {
+  height: 0;
+  flex: 1 1 auto;
+  min-height: 0;
+  background: #ffffff;
+}
+
+.aigc-agreement-document {
+  min-height: 100%;
+  padding: 20px 16px calc(24px + env(safe-area-inset-bottom));
+  box-sizing: border-box;
+}
+
+.aigc-agreement-state {
+  min-height: 240px;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  padding: 24px;
+  color: #7b8798;
+  font-size: 14px;
+  line-height: 22px;
+  box-sizing: border-box;
+}
+
+.aigc-agreement-retry {
+  width: 120px;
+  height: 42px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  margin: 16px 0 0;
+  padding: 0;
+  border-radius: 999px;
+  background: #102942;
+  color: #ffffff;
+  font-size: 14px;
+  line-height: 20px;
+  font-weight: 800;
+}
+
+.aigc-agreement-retry::after {
+  border: 0;
+}