feat(#365): add pin support for models with pinned section at top (#414)

* feat(#365): add pin support for models with pinned section at top

* fix(#365): stub Pinned Models methods in E2eIntegrationTest

* fix(#365): use state flow for pin/unpin, add max cap, add ViewModel tests

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/data/model/ModelOption.kt

@@ -16,3 +16,8 @@ data class ModelProvider(
     val auth_type: String?,
     val warning: String?,
 )
+
+data class PinnedModel(
+    val providerSlug: String,
+    val modelName: String,
+)