refactor: add default ollama provider config and set it to codellama

lua/plugins/avante.lua

@@ -7,6 +7,10 @@ return {
             -- add any opts here
             -- for example
             provider = "mistral",
+            ollama = {
+                model = "codellama",
+                endpoint = "http://127.0.0.1:11434",
+            },
             vendors = {
                 mistral = {
                     __inherited_from = "openai",