fix: pick a free port for the desktop backend when 30001 is taken (#1663)

env.catalog.json

@@ -71,7 +71,6 @@
       "group": "server",
       "description": "SSH agent socket used for hosts set to agent auth when they do not name their own socket."
     },
-
     {
       "name": "ENABLE_SSL",
       "group": "https",
@@ -108,7 +107,6 @@
       "internal": true,
       "description": "Set by the image when nginx serves HTTPS in front of the backend."
     },
-
     {
       "name": "DATABASE_DIALECT",
       "group": "database",
@@ -161,7 +159,6 @@
       "internal": true,
       "description": "Where database migrations are read from. Set by the image."
     },
-
     {
       "name": "JWT_SECRET",
       "group": "secrets",
@@ -204,7 +201,6 @@
       "secret": true,
       "description": "Only read to move data from installs older than 2.5. Never change it on an install that has it."
     },
-
     {
       "name": "ALLOW_PASSWORD_LOGIN",
       "group": "auth",
@@ -283,7 +279,6 @@
       "group": "auth",
       "description": "JSON map from proxy roles to Termix roles, like {\"admins\":[\"admin\"],\"staff\":[\"user\"]}. Required when trusted proxy login is on."
     },
-
     {
       "name": "TRUSTED_PROXIES",
       "group": "proxy",
@@ -315,7 +310,6 @@
       "group": "proxy",
       "description": "Comma separated hosts that skip the proxy."
     },
-
     {
       "name": "LOG_LEVEL",
       "group": "logging",
@@ -355,7 +349,6 @@
       "deprecated": "the session-recording plugin setting",
       "description": "Only read once to carry a 2.8 value into the session-recording plugin."
     },
-
     {
       "name": "TERMIX_PLUGIN_REGISTRY_URL",
       "group": "plugins",
@@ -406,7 +399,6 @@
       "internal": true,
       "description": "Set by npm run dev."
     },
-
     {
       "name": "ENABLE_INSECURE_MODE",
       "group": "desktop",
@@ -435,6 +427,12 @@
       "internal": true,
       "description": "Set by the desktop app when it runs its own backend."
     },
+    {
+      "name": "EMBEDDED_BACKEND_PORT",
+      "group": "desktop",
+      "internal": true,
+      "description": "Set by the desktop app to the port its own backend listens on. 30001 unless another program holds it."
+    },
     {
       "name": "TERMIX_DATA_DIR",
       "group": "desktop",
@@ -459,14 +457,12 @@
       "internal": true,
       "description": "Set by Flatpak. The desktop app links new versions instead of installing them."
     },
-
     {
       "name": "DESKTOP_SESSION",
       "group": "desktop",
       "internal": true,
       "description": "Read on Linux to pick the password store."
     },
-
     {
       "name": "VITE_BASE_PATH",
       "group": "internal",