fix: refresh loopback dashboard token after restart (#568)

* fix: refresh loopback dashboard token after restart

The gateway regenerates its ephemeral session token on every restart, so the
token the app persisted becomes stale. After a dashboard restart REST calls
401 and the WebSocket auto-reconnect loop hangs in AUTH_EXPIRED until the user
manually re-authenticates.

- Add DashboardSessionTokenRefresher: re-reads the injected
  window.__HERMES_SESSION_TOKEN__ from the dashboard SPA and writes it back to
  AuthManager.
- TokenRefreshAuthenticator: on a 401 retry, scrape a fresh token from the
  dashboard and retry instead of giving up.
- HermesWsClient: refresh the token before each non-gated WebSocket handshake so
  reconnects don't get stuck on a stale token; guard serverStore read against
  IllegalStateException.

Covers the loopback (--insecure) deployment path; gated/ticket mode is untouched.

* fix: harden dashboard token refresher (sync, body cap, blank-token test)

Second-opinion review flagged robustness gaps (no correctness/security
regressions in the happy path):

- DashboardSessionTokenRefresher.refresh(): @Synchronized to dedupe
  concurrent 401 / reconnect storms instead of each firing its own GET.
- Cap SPA HTML read at 64 KiB before regex scan (defensive against OOM on
  low-end devices); we only need the injected token near the document top.
- HermesWsClient: log (not silently swallow) the transient uninitialized
  serverStore case so a real misconfig is still visible.
- Add test: blank-injected token returns null.

---------

Co-authored-by: M57 <m57@hermes-control.app>

app/src/main/java/com/m57/hermescontrol/data/remote/DashboardSessionTokenRefresher.kt

@@ -0,0 +1,51 @@
+package com.m57.hermescontrol.data.remote
+
+import com.m57.hermescontrol.data.local.AuthManager
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import okio.Buffer
+
+internal object DashboardSessionTokenRefresher {
+    private val tokenPattern = Regex("""__HERMES_SESSION_TOKEN__\s*=\s*"([^"]+)"""")
+
+    // Synchronized so concurrent 401s / reconnect storms don't each fire a
+    // redundant GET at the dashboard SPA (thundering-herd guard).
+    @Synchronized
+    fun refresh(): String? =
+        try {
+            val token = fetch(AuthManager.baseUrl(), OkHttpProvider.probe) ?: return null
+            AuthManager.setToken(token)
+            token
+        } catch (_: Exception) {
+            null
+        }
+
+    internal fun fetch(
+        baseUrl: String,
+        client: OkHttpClient,
+    ): String? =
+        try {
+            val request = Request.Builder().url(baseUrl).get().build()
+            client.newCall(request).execute().use { response ->
+                if (!response.isSuccessful) return null
+                // Cap the read — the SPA HTML can be large, and we only need the
+                // injected token near the top of the document. Reading the whole
+                // body into a String risks OOM on low-end devices.
+                val html =
+                    response.body.source().use { source ->
+                        val buffer = Buffer()
+                        source.read(buffer, MAX_BODY_BYTES)
+                        buffer.readUtf8()
+                    }
+                tokenPattern
+                    .find(html)
+                    ?.groupValues
+                    ?.getOrNull(1)
+                    ?.takeIf { it.isNotBlank() }
+            }
+        } catch (_: Exception) {
+            null
+        }
+
+    private const val MAX_BODY_BYTES: Long = 64 * 1024
+}

app/src/main/java/com/m57/hermescontrol/data/remote/TokenRefreshAuthenticator.kt

@@ -18,8 +18,9 @@ object TokenRefreshAuthenticator : Authenticator {
         // shared CookieJar (issue #470), so OkHttp re-attaches it on retry
         // without any manual header manipulation here.
 
-        // Loopback mode: re-assert the Bearer token if the request lacked it
-        // (or it drifted from the current stored token).
+        // Loopback mode: a dashboard restart invalidates the saved ephemeral
+        // token. First reuse a token another request may already have refreshed;
+        // otherwise extract the current token from the dashboard SPA.
         val token = AuthManager.getToken()
         val requestAuth = response.request.header("Authorization")
         val currentAuthHeader = "Bearer $token"
@@ -29,6 +30,11 @@ object TokenRefreshAuthenticator : Authenticator {
                 .header("Authorization", currentAuthHeader)
                 .build()
         }
-        return null
+
+        val refreshedToken = DashboardSessionTokenRefresher.refresh() ?: return null
+        return response.request
+            .newBuilder()
+            .header("Authorization", "Bearer $refreshedToken")
+            .build()
     }
 }

app/src/main/java/com/m57/hermescontrol/data/ws/HermesWsClient.kt

@@ -4,6 +4,7 @@ import android.util.Log
 import androidx.annotation.VisibleForTesting
 import com.m57.hermescontrol.BuildConfig
 import com.m57.hermescontrol.data.local.AuthManager
+import com.m57.hermescontrol.data.remote.DashboardSessionTokenRefresher
 import com.m57.hermescontrol.data.remote.NetworkMonitor
 import com.m57.hermescontrol.data.remote.OkHttpProvider
 import kotlinx.coroutines.CompletableDeferred
@@ -234,8 +235,21 @@ object HermesWsClient {
      * and ticket refresh failed or cannot be performed.
      */
     private fun refreshWsTicketIfNeeded(): Boolean {
-        val isGated = AuthManager.serverStore.getLatestState().wsAuthParam == "ticket"
+        val isGated =
+            try {
+                AuthManager.serverStore.getLatestState().wsAuthParam == "ticket"
+            } catch (_: IllegalStateException) {
+                // serverStore not initialized yet (transient early call); treat
+                // as loopback so a stale-token refresh still runs. Log so a real
+                // misconfiguration isn't silently swallowed.
+                Log.w(TAG, "serverStore uninitialized during WS handshake; assuming non-gated")
+                false
+            }
         if (!isGated) {
+            // The loopback dashboard token is regenerated on every server
+            // restart. Refresh it before each WebSocket handshake so automatic
+            // reconnect does not get stuck in AUTH_EXPIRED with a stale token.
+            DashboardSessionTokenRefresher.refresh()
             return true
         }