Add Llama 3.2 1B and Gemma 3 4B model presets

Add downloadable model presets for Llama 3.2 1B and Gemma 3 4B to the
preset model selection screen. These models can now be downloaded
directly from HuggingFace within the app.

Author: kirklandsign

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/ModelDownloadConfig.kt

@@ -35,6 +35,22 @@ object ModelDownloadConfig {
             tokenizerUrl = "https://ossci-android.s3.amazonaws.com/executorch/stories/snapshot-20260114/tokenizer.model",
             tokenizerFilename = "tokenizer.model",
             modelType = ModelType.LLAMA_3
+        ),
+        "llama" to ModelInfo(
+            displayName = "Llama 3.2 1B",
+            modelUrl = "https://huggingface.co/executorch-community/Llama-3.2-1B-ET/resolve/main/llama3_2-1B.pte",
+            modelFilename = "llama3_2-1B.pte",
+            tokenizerUrl = "https://huggingface.co/executorch-community/Llama-3.2-1B-ET/resolve/main/tokenizer.model",
+            tokenizerFilename = "tokenizer.model",
+            modelType = ModelType.LLAMA_3
+        ),
+        "gemma" to ModelInfo(
+            displayName = "Gemma 3 4B",
+            modelUrl = "https://huggingface.co/pytorch/gemma-3-4b-it-HQQ-INT8-INT4/resolve/main/model.pte",
+            modelFilename = "model.pte",
+            tokenizerUrl = "https://huggingface.co/pytorch/gemma-3-4b-it-HQQ-INT8-INT4/resolve/main/tokenizer.json",
+            tokenizerFilename = "tokenizer.json",
+            modelType = ModelType.GEMMA_3
         )
     )