fix(proxy): enable gzip compression for non-streaming proxy requests

Non-streaming requests were forced to use `Accept-Encoding: identity`,
preventing upstream response compression and increasing bandwidth usage.

Now only streaming requests conservatively keep `identity` to avoid
decompression errors on interrupted SSE streams. Non-streaming requests
let reqwest auto-negotiate gzip and transparently decompress responses.

src-tauri/Cargo.lock

@@ -137,6 +137,18 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "async-compression"
+version = "0.4.41"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0f9ee0f6e02ffd7ad5816e9464499fba7b3effd01123b515c41d1697c43dad1"
+dependencies = [
+ "compression-codecs",
+ "compression-core",
+ "pin-project-lite",
+ "tokio",
+]
+
 [[package]]
 name = "async-executor"
 version = "1.14.0"
@@ -798,6 +810,23 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "compression-codecs"
+version = "0.4.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eb7b51a7d9c967fc26773061ba86150f19c50c0d65c887cb1fbe295fd16619b7"
+dependencies = [
+ "compression-core",
+ "flate2",
+ "memchr",
+]
+
+[[package]]
+name = "compression-core"
+version = "0.4.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "75984efb6ed102a0d42db99afb6c1948f0380d1d91808d5529916e6c08b49d8d"
+
 [[package]]
 name = "concurrent-queue"
 version = "2.5.0"
@@ -5988,13 +6017,18 @@ version = "0.6.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d4e6559d53cc268e5031cd8429d05415bc4cb4aefc4aa5d6cc35fbf5b924a1f8"
 dependencies = [
+ "async-compression",
  "bitflags 2.11.0",
  "bytes",
+ "futures-core",
  "futures-util",
  "http",
  "http-body",
+ "http-body-util",
  "iri-string",
  "pin-project-lite",
+ "tokio",
+ "tokio-util",
  "tower 0.5.3",
  "tower-layer",
  "tower-service",