refactor(backend): migrate to tauri v2 sidecars and resolve pipe deadlocks

- Replace tokio::process with tauri_plugin_shell sidecar API for native cross-compilation bundle execution.
- Implement non-blocking stdout/stderr multiplexing in yt-dlp spawn to prevent OS pipe buffer deadlocks.
- Refactor capabilities to restrict execution explicitly to sidecars instead of wildcards.
- Rename local binaries to strictly adhere to target-triple architecture suffixes.
- Drop manual get_binary_name path resolutions in favor of Tauri's externalBin bundler.

src-tauri/Cargo.lock

@@ -1256,6 +1256,7 @@ dependencies = [
  "tauri-plugin-dialog",
  "tauri-plugin-notification",
  "tauri-plugin-opener",
+ "tauri-plugin-shell",
  "tauri-plugin-single-instance",
  "tempfile",
  "thiserror 2.0.18",
@@ -3032,6 +3033,16 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "os_pipe"
+version = "1.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d8fae84b431384b68627d0f9b3b1245fcf9f46f6c0e3dc902e9dce64edd1967"
+dependencies = [
+ "libc",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "pango"
 version = "0.18.3"
@@ -4065,12 +4076,44 @@ dependencies = [
  "digest",
 ]
 
+[[package]]
+name = "shared_child"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e362d9935bc50f019969e2f9ecd66786612daae13e8f277be7bfb66e8bed3f7"
+dependencies = [
+ "libc",
+ "sigchld",
+ "windows-sys 0.60.2",
+]
+
 [[package]]
 name = "shlex"
 version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8fadd59c855ef2080decdef8ff161eb6661b86933c9d82e5ba29dc602a55aba"
 
+[[package]]
+name = "sigchld"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47106eded3c154e70176fc83df9737335c94ce22f821c32d17ed1db1f83badb1"
+dependencies = [
+ "libc",
+ "os_pipe",
+ "signal-hook",
+]
+
+[[package]]
+name = "signal-hook"
+version = "0.3.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d881a16cf4426aa584979d30bd82cb33429027e42122b169753d6ef1085ed6e2"
+dependencies = [
+ "libc",
+ "signal-hook-registry",
+]
+
 [[package]]
 name = "signal-hook-registry"
 version = "1.4.8"
@@ -4631,6 +4674,27 @@ dependencies = [
  "zbus",
 ]
 
+[[package]]
+name = "tauri-plugin-shell"
+version = "2.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8457dbf9e2bab1edd8df22bb2c20857a59a9868e79cb3eac5ed639eec4d0c73b"
+dependencies = [
+ "encoding_rs",
+ "log 0.4.32",
+ "open",
+ "os_pipe",
+ "regex 1.12.4",
+ "schemars 0.8.22",
+ "serde",
+ "serde_json",
+ "shared_child",
+ "tauri",
+ "tauri-plugin",
+ "thiserror 2.0.18",
+ "tokio",
+]
+
 [[package]]
 name = "tauri-plugin-single-instance"
 version = "2.4.2"