feat(server): add OXICLOUD_REUSE_PORT env parameter (false by default)

initially server was accepting multiple instances on same port (Linux and MacOS only)
    this can create issues during development (if a dev forget another running instance...)

    Add OXICLOUD_REUSE_PORT variable to activate it, so only admins knowing this feature can activate itt
    (permits multiple instance + let the OS schedduler to decide which process will handle a request)

    if not enabled, other instance will receive exit with a:
    `Error: Os { code: 48, kind: AddrInUse, message: "Address already in use" }`

example.env

@@ -34,6 +34,14 @@ OXICLOUD_SERVER_HOST=127.0.0.1
 # Maximum upload size in bytes (default: 10 GB on 64-bit)
 #OXICLOUD_MAX_UPLOAD_SIZE=10737418240
 
+# Allow multiple processes to bind to the same port (SO_REUSEPORT).
+# DISABLED by default — leaving this off means a second accidental instance
+# will fail immediately with "address already in use", which is the safe behaviour.
+# Enable ONLY when you deliberately run several worker processes in parallel
+# (e.g. behind a process supervisor or during a zero-downtime rolling restart).
+# Not supported on Windows.
+#OXICLOUD_REUSE_PORT=false
+
 # -----------------------------------------------------------------------------
 # DATABASE CONFIGURATION
 # -----------------------------------------------------------------------------