Add structured headers to the PHP pages layer

Documents each tab's purpose, what it renders, and which endpoints it polls.
Pages that start with markup get the header in a <?php ?> block so it never
reaches the browser.

Also corrects the layer diagram in README-unraid.md: eight of eleven pages hold
no PHP logic and poll api/ for everything — only auth, monitor and scheduler
require an include/ file directly.

Plugin/unraid/pages/rsync.php

@@ -1,3 +1,42 @@
+<?php
+// ═══════════════════════════════════════════════════════════════════════════════════════════════
+// PURPOSE
+//   Rsync tab. Sync profiles, share lists, transfer progress, per-run history, and manual
+//   sync triggers.
+//
+// DESIGN PRINCIPLES
+//   Pure view — profile and status data from api/rsync.php, profile edits through
+//   api/rsync_profiles.php, manual runs through api/manual_sync.php.
+//
+//   Progress polls fast (2s) while a transfer is live and falls back to the slow interval
+//   otherwise, so an idle page is not hammering the endpoint.
+//
+//   Profiles are edited as structured data, not as raw rsync flags typed by hand.
+//
+// OPERATIONAL SAFEGUARDS
+//   Manual sync is confirmed before it fires. A sync moves real data between two machines and
+//   is not something to trigger with a stray click.
+//
+//   The page shows the global RSYNC_ENABLED gate alongside the per-tier toggles, so a run
+//   that will be skipped by the gate is visibly skipped rather than silently doing nothing.
+//
+//   Heavy escaping throughout — share paths, profile names and rsync output all render as
+//   text, never as markup.
+//
+//   The page does not compose rsync flags. Deletion semantics in particular are owned by
+//   Rsync/rsync.sh, where the pass-1-must-complete interlock lives.
+//
+// RENDERS
+//   Profile editor, share lists, live transfer progress, run history, manual sync controls
+//
+// DEPENDS ON
+//   api/rsync.php             status, polled 2s live / 30s idle
+//   api/rsync_profiles.php    profile read and write
+//   api/manual_sync.php       manual run trigger
+//   api/rsync_win_arrays.php  share array editing
+//   api/flag_toggle.php       enable/disable toggles
+//   api/confform.php          inline conf edits
+?>
 <style>
 .vv-ry-card    { background:#161616;border:1px solid #2a2a2a;border-radius:6px;padding:10px 12px;min-width:0; }
 .vv-ry-sec     { font-size:10px;font-weight:bold;color:#444;letter-spacing:.07em;text-transform:uppercase;margin-bottom:6px; }