Replace Anthropic library (anthropic-rs -> anthropic) and switch default recommended model (claude-3-5-sonnet-20240620 -> claude-3-7-sonnet-20250219)

Fixes https://github.com/etkecc/baibot/issues/22

Ultimate related to `anthropic-rs` hardcoding models as enumeration variants in the code
and not updating them. See:
- https://github.com/roushou/mesh/issues/1
- https://github.com/roushou/mesh/pull/2

https://github.com/cortesi/misanthropy was also considered as an
alternative, but it did not allow configuring the base API URL like our
old Anthropic library (`anthropic-rs`) and like our new choice (`anthropic`).
We'd rather not lose support for this, so we're going with the `anthropic` library.

src/agent/provider/anthropic/utils.rs

@@ -1,8 +1,8 @@
-use anthropic_rs::completion::message::{Content, ContentType, Message, MessageRequest, Role};
+use anthropic::types::{ContentBlock, Message, MessagesRequest, MessagesRequestBuilder, Role};
 
 use crate::conversation::llm::{Author as LLMAuthor, Message as LLMMessage};
 
-pub(super) fn create_anthropic_message_request(llm_messages: Vec<LLMMessage>) -> MessageRequest {
+pub(super) fn create_anthropic_message_request(llm_messages: Vec<LLMMessage>) -> MessagesRequest {
     let mut messages = vec![];
 
     for message in llm_messages {
@@ -14,8 +14,7 @@ pub(super) fn create_anthropic_message_request(llm_messages: Vec<LLMMessage>) ->
             }
         };
 
-        let content = vec![Content {
-            content_type: ContentType::Text,
+        let content = vec![ContentBlock::Text {
             text: message.message_text,
         }];
 
@@ -24,9 +23,9 @@ pub(super) fn create_anthropic_message_request(llm_messages: Vec<LLMMessage>) ->
         messages.push(message);
     }
 
-    MessageRequest {
-        stream: false,
-        messages,
-        ..Default::default()
-    }
+    MessagesRequestBuilder::default()
+        .messages(messages)
+        .stream(false)
+        .build()
+        .expect("Failed to build messages request")
 }