fix(app-proxy): make the SPA shell identical for every visitor (#3112)

fluxer_app_proxy/Cargo.toml

@@ -16,6 +16,7 @@ rand = "0.10"
 reqwest = { version = "0.13.5", default-features = false, features = ["json", "rustls", "stream", "gzip", "brotli", "deflate"] }
 serde = { version = "1.0.229", features = ["derive"] }
 serde_json = "1.0.151"
+sha2 = "0.11.0"
 tokio = { version = "1.53.1", features = ["macros", "net", "rt-multi-thread", "signal", "time", "fs"] }
 tokio-util = { version = "0.7.19", features = ["io"] }
 tower = { version = "0.5.3", features = ["util"] }