feat(chat): render LaTeX formulas natively (#939)

* feat(chat): render LaTeX formulas

Support native inline and display math with accessible Compose rendering.

* perf(chat): reuse LaTeX parsing state

Share one measurer per message and skip redundant math splitting.

app/build.gradle.kts

@@ -165,6 +165,11 @@ dependencies {
     implementation(libs.retrofit.converter.kotlinx.serialization)
     implementation(libs.kotlinx.serialization.json)
 
+    // Native Compose LaTeX rendering
+    implementation(libs.latex.base)
+    implementation(libs.latex.parser)
+    implementation(libs.latex.renderer)
+
     // Image loading
     implementation(libs.coil.compose)
     implementation(libs.coil.gif)