Update to latest Mistral AI API (v1.0.0)

- Replace closed Model enum with flexible string-based Model type
  with constructor methods for all current models (Mistral Large 3,
  Small 4, Magistral, Codestral, Devstral, Pixtral, Voxtral, etc.)
- Add new API endpoints: FIM completions, Files, Fine-tuning, Batch
  jobs, OCR, Audio transcription, Moderations/Classifications, and
  Agent completions (sync + async for all)
- Add new chat fields: frequency_penalty, presence_penalty, stop,
  n, parallel_tool_calls, reasoning_effort, min_tokens, json_schema
  response format
- Add embedding fields: output_dimension, output_dtype
- Tool parameters now accept raw JSON Schema (serde_json::Value)
  instead of limited enum types
- Add tool call IDs and Required tool choice variant
- Add DELETE HTTP method support and multipart file upload
- Bump thiserror to v2, add reqwest multipart feature
- Remove strum dependency (no longer needed)
- Update all tests and examples for new API

examples/chat_async.rs

@@ -1,5 +1,5 @@
 use mistralai_client::v1::{
-    chat::{ChatMessage, ChatMessageRole, ChatParams},
+    chat::{ChatMessage, ChatParams},
     client::Client,
     constants::Model,
 };
@@ -9,14 +9,12 @@ async fn main() {
     // This example suppose you have set the `MISTRAL_API_KEY` environment variable.
     let client = Client::new(None, None, None, None).unwrap();
 
-    let model = Model::OpenMistral7b;
-    let messages = vec![ChatMessage {
-        role: ChatMessageRole::User,
-        content: "Just guess the next word: \"Eiffel ...\"?".to_string(),
-        tool_calls: None,
-    }];
+    let model = Model::mistral_small_latest();
+    let messages = vec![ChatMessage::new_user_message(
+        "Just guess the next word: \"Eiffel ...\"?",
+    )];
     let options = ChatParams {
-        temperature: 0.0,
+        temperature: Some(0.0),
         random_seed: Some(42),
         ..Default::default()
     };
@@ -29,5 +27,4 @@ async fn main() {
         "{:?}: {}",
         result.choices[0].message.role, result.choices[0].message.content
     );
-    // => "Assistant: Tower. The Eiffel Tower is a famous landmark in Paris, France."
 }