feat(core): add axum HTTP router scaffold with auth middleware and stealth handoff

Add http feature flag with axum, hyper, hyper-util, tower, and http-body-util
dependencies. Create http module with auth middleware (extracts Bearer token,
calls IdentityProvider::resolve_from_token, attaches Identity to extensions)
and router scaffold (default 404 fallback, no operational routes yet). Replace
send_fake_nginx_404 with axum router handoff when http feature is enabled;
fake 404 behavior preserved when http is disabled. Wire HttpInterface with
build_router() method and pass IdentityProvider through Server to handle_connection.

Cargo.lock

@@ -77,8 +77,12 @@ dependencies = [
  "anyhow",
  "arc-swap",
  "async-trait",
+ "axum",
  "futures",
  "hex",
+ "http-body-util",
+ "hyper",
+ "hyper-util",
  "ipnetwork",
  "iroh",
  "rand 0.10.1",
@@ -97,6 +101,7 @@ dependencies = [
  "tokio",
  "tokio-rustls",
  "tokio-util",
+ "tower",
  "tracing",
  "url",
  "webpki-roots 0.26.11",
@@ -402,6 +407,58 @@ dependencies = [
  "fs_extra",
 ]
 
+[[package]]
+name = "axum"
+version = "0.8.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "31b698c5f9a010f6573133b09e0de5408834d0c82f8d7475a89fc1867a71cd90"
+dependencies = [
+ "axum-core",
+ "bytes",
+ "form_urlencoded",
+ "futures-util",
+ "http 1.4.1",
+ "http-body",
+ "http-body-util",
+ "hyper",
+ "hyper-util",
+ "itoa",
+ "matchit",
+ "memchr",
+ "mime",
+ "percent-encoding",
+ "pin-project-lite",
+ "serde_core",
+ "serde_json",
+ "serde_path_to_error",
+ "serde_urlencoded",
+ "sync_wrapper",
+ "tokio",
+ "tower",
+ "tower-layer",
+ "tower-service",
+ "tracing",
+]
+
+[[package]]
+name = "axum-core"
+version = "0.5.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08c78f31d7b1291f7ee735c1c6780ccde7785daae9a9206026862dab7d8792d1"
+dependencies = [
+ "bytes",
+ "futures-core",
+ "http 1.4.1",
+ "http-body",
+ "http-body-util",
+ "mime",
+ "pin-project-lite",
+ "sync_wrapper",
+ "tower-layer",
+ "tower-service",
+ "tracing",
+]
+
 [[package]]
 name = "backon"
 version = "1.6.0"
@@ -2380,6 +2437,12 @@ dependencies = [
  "regex-automata",
 ]
 
+[[package]]
+name = "matchit"
+version = "0.8.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47e1ffaa40ddd1f3ed91f717a33c8c0ee23fff369e3aa8772b9605cc1d22f4c3"
+
 [[package]]
 name = "md5"
 version = "0.7.0"
@@ -2392,6 +2455,12 @@ version = "2.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6b947ae49db0d222b1dbc6b113ce7248a3fc3a6ca21b696717bfc000ba4484d8"
 
+[[package]]
+name = "mime"
+version = "0.3.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
@@ -4111,6 +4180,17 @@ dependencies = [
  "zmij",
 ]
 
+[[package]]
+name = "serde_path_to_error"
+version = "0.1.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10a9ff822e371bb5403e391ecd83e182e0e77ba7f6fe0160b795797109d1b457"
+dependencies = [
+ "itoa",
+ "serde",
+ "serde_core",
+]
+
 [[package]]
 name = "serde_urlencoded"
 version = "0.7.1"
@@ -4738,6 +4818,7 @@ dependencies = [
  "tokio",
  "tower-layer",
  "tower-service",
+ "tracing",
 ]
 
 [[package]]