feat: enforce dynamic browser extension pairing security

- Generate random pairing token in AppSettings

- Update LocalExtensionServer to strict check token on non-OPTIONS endpoints

- Add GET /ping endpoint for extension connection verification

- Redesign Integration settings pane with modern step-by-step UI and Toast notifications

- Harden media extraction and aria2 engine paths

- Update IP resolution with getaddrinfo

Sources/Firelink/Aria2DownloadEngine.swift

@@ -56,21 +56,14 @@ final class Aria2DownloadEngine {
         let candidates = [
             "/opt/homebrew/bin/aria2c",
             "/usr/local/bin/aria2c",
-            "/usr/bin/aria2c"
+            "/usr/bin/aria2c",
+            "/opt/local/bin/aria2c"
         ]
 
         if let found = candidates.first(where: { FileManager.default.isExecutableFile(atPath: $0) }) {
             return URL(fileURLWithPath: found)
         }
 
-        let path = ProcessInfo.processInfo.environment["PATH"] ?? ""
-        for folder in path.split(separator: ":") {
-            let candidate = URL(fileURLWithPath: String(folder)).appendingPathComponent("aria2c")
-            if FileManager.default.isExecutableFile(atPath: candidate.path) {
-                return candidate
-            }
-        }
-
         return nil
     }