feat(proxy): add streaming SSE transform and thinking parameter support

New features:
- Add OpenAI → Anthropic SSE streaming response transformation
- Support thinking parameter detection for reasoning model selection
- Add ANTHROPIC_REASONING_MODEL config option for extended thinking

Changes:
- streaming.rs: Implement SSE event parsing and Anthropic format conversion
- transform.rs: Add thinking detection logic and reasoning model mapping
- handlers.rs: Integrate streaming transform for OpenRouter compatibility
- Cargo.toml: Add async-stream and bytes dependencies

src-tauri/Cargo.lock

@@ -257,6 +257,28 @@ dependencies = [
  "windows-sys 0.61.1",
 ]
 
+[[package]]
+name = "async-stream"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b5a71a6f37880a80d1d7f19efd781e4b5de42c88f0722cc13bcb6cc2cfe8476"
+dependencies = [
+ "async-stream-impl",
+ "futures-core",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "async-stream-impl"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c7c24de15d275a1ecfd47a380fb4d5ec9bfe0933f309ed5e705b775596a3574d"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.106",
+]
+
 [[package]]
 name = "async-task"
 version = "4.7.1"
@@ -676,9 +698,11 @@ name = "cc-switch"
 version = "3.8.1"
 dependencies = [
  "anyhow",
+ "async-stream",
  "auto-launch",
  "axum",
  "base64 0.22.1",
+ "bytes",
  "chrono",
  "dirs 5.0.1",
  "futures",