refactor: move download/decryption to backend to fix UI freezing

Now implements streaming download+decryption entirely in Rust:
- Added reqwest/tokio/futures-util dependencies
- Created StreamingDecryptor for chunk-by-chunk decryption
- New download_and_decrypt_track command streams to disk directly
- Frontend simplified to single invoke() call

src-tauri/Cargo.lock

@@ -8,9 +8,11 @@ version = "0.1.0"
 dependencies = [
  "blowfish",
  "byteorder",
+ "futures-util",
  "id3",
  "md5",
  "metaflac",
+ "reqwest",
  "serde",
  "serde_json",
  "tauri",
@@ -22,6 +24,7 @@ dependencies = [
  "tauri-plugin-process",
  "tauri-plugin-sql",
  "tauri-plugin-store",
+ "tokio",
 ]
 
 [[package]]
@@ -659,7 +662,7 @@ dependencies = [
  "bitflags 2.9.4",
  "core-foundation 0.10.1",
  "core-graphics-types",
- "foreign-types",
+ "foreign-types 0.5.0",
  "libc",
 ]
 
@@ -1192,6 +1195,15 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
 
+[[package]]
+name = "foreign-types"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f6f339eb8adc052cd2ca78910fda869aefa38d22d5cb648e6485e4d3fc06f3b1"
+dependencies = [
+ "foreign-types-shared 0.1.1",
+]
+
 [[package]]
 name = "foreign-types"
 version = "0.5.0"
@@ -1199,7 +1211,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d737d9aa519fb7b749cbc3b962edcf310a8dd1f4b67c91c4f83975dbdd17d965"
 dependencies = [
  "foreign-types-macros",
- "foreign-types-shared",
+ "foreign-types-shared 0.3.1",
 ]
 
 [[package]]
@@ -1213,6 +1225,12 @@ dependencies = [
  "syn 2.0.106",
 ]
 
+[[package]]
+name = "foreign-types-shared"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "00b0228411908ca8685dba7fc2cdd70ec9990a6e753e89b6ac91a84c40fbaf4b"
+
 [[package]]
 name = "foreign-types-shared"
 version = "0.3.1"
@@ -1844,6 +1862,22 @@ dependencies = [
  "webpki-roots",
 ]
 
+[[package]]
+name = "hyper-tls"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70206fc6890eaca9fde8a0bf71caa2ddfc9fe045ac9e5c70df101a7dbde866e0"
+dependencies = [
+ "bytes",
+ "http-body-util",
+ "hyper",
+ "hyper-util",
+ "native-tls",
+ "tokio",
+ "tokio-native-tls",
+ "tower-service",
+]
+
 [[package]]
 name = "hyper-util"
 version = "0.1.17"
@@ -2464,6 +2498,23 @@ dependencies = [
  "windows-sys 0.60.2",
 ]
 
+[[package]]
+name = "native-tls"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "87de3442987e9dbec73158d5c715e7ad9072fda936bb03d19d7fa10e00520f0e"
+dependencies = [
+ "libc",
+ "log",
+ "openssl",
+ "openssl-probe",
+ "openssl-sys",
+ "schannel",
+ "security-framework",
+ "security-framework-sys",
+ "tempfile",
+]
+
 [[package]]
 name = "ndk"
 version = "0.9.0"
@@ -2858,6 +2909,50 @@ dependencies = [
  "pathdiff",
 ]
 
+[[package]]
+name = "openssl"
+version = "0.10.73"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8505734d46c8ab1e19a1dce3aef597ad87dcb4c37e7188231769bd6bd51cebf8"
+dependencies = [
+ "bitflags 2.9.4",
+ "cfg-if",
+ "foreign-types 0.3.2",
+ "libc",
+ "once_cell",
+ "openssl-macros",
+ "openssl-sys",
+]
+
+[[package]]
+name = "openssl-macros"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a948666b637a0f465e8564c73e89d4dde00d72d4d473cc972f390fc3dcee7d9c"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.106",
+]
+
+[[package]]
+name = "openssl-probe"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d05e27ee213611ffe7d6348b942e8f942b37114c00cc03cec254295a4a17852e"
+
+[[package]]
+name = "openssl-sys"
+version = "0.9.109"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "90096e2e47630d78b7d1c20952dc621f957103f8bc2c8359ec81290d75238571"
+dependencies = [
+ "cc",
+ "libc",
+ "pkg-config",
+ "vcpkg",
+]
+
 [[package]]
 name = "option-ext"
 version = "0.2.0"
@@ -3579,10 +3674,12 @@ dependencies = [
  "http-body-util",
  "hyper",
  "hyper-rustls",
+ "hyper-tls",
  "hyper-util",
  "js-sys",
  "log",
  "mime",
+ "native-tls",
  "percent-encoding",
  "pin-project-lite",
  "quinn",
@@ -3593,6 +3690,7 @@ dependencies = [
  "serde_urlencoded",
  "sync_wrapper",
  "tokio",
+ "tokio-native-tls",
  "tokio-rustls",
  "tokio-util",
  "tower",
@@ -3755,6 +3853,15 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "schannel"
+version = "0.1.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1f29ebaa345f945cec9fbbc532eb307f0fdad8161f281b6369539c8d84876b3d"
+dependencies = [
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "schemars"
 version = "0.8.22"
@@ -3818,6 +3925,29 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
+[[package]]
+name = "security-framework"
+version = "2.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "897b2245f0b511c87893af39b033e5ca9cce68824c4d7e7630b5a1d339658d02"
+dependencies = [
+ "bitflags 2.9.4",
+ "core-foundation 0.9.4",
+ "core-foundation-sys",
+ "libc",
+ "security-framework-sys",
+]
+
+[[package]]
+name = "security-framework-sys"
+version = "2.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49db231d56a190491cb4aeda9527f1ad45345af50b0851622a7adb8c03b01c32"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
 [[package]]
 name = "selectors"
 version = "0.24.0"
@@ -4116,7 +4246,7 @@ dependencies = [
  "bytemuck",
  "cfg_aliases",
  "core-graphics",
- "foreign-types",
+ "foreign-types 0.5.0",
  "js-sys",
  "log",
  "objc2 0.5.2",
@@ -5085,6 +5215,16 @@ dependencies = [
  "syn 2.0.106",
 ]
 
+[[package]]
+name = "tokio-native-tls"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbae76ab933c85776efabc971569dd6119c580d8f5d448769dec1764bf796ef2"
+dependencies = [
+ "native-tls",
+ "tokio",
+]
+
 [[package]]
 name = "tokio-rustls"
 version = "0.26.4"