Fix NFS parser showing /etc/exports example comments as disabled exports

The default nfs-kernel-server package ships /etc/exports with commented
example lines like '# /srv/homes hostname1(rw,...)'. The old parser
treated any comment containing a path as a disabled export, so these
examples showed up in the UI.

Fix: use a distinct '## ' prefix (double-hash + space) for exports that
MicroNAS disables. The parser now only recognises '## /path ...' as a
disabled export — any other '#' line is left as a plain comment.
_write_exports updated to use the same prefix when toggling off.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.py

@@ -142,8 +142,13 @@ def add_smb_share(name, path, valid_users):
 
 # ===== NFS =====
 
+_DISABLED_PREFIX = '## '   # marker MicroNAS uses for disabled exports
+
+
 def _parse_exports():
-    """Parse /etc/exports preserving blanks, comments, and disabled (commented-out) exports."""
+    """Parse /etc/exports. Only lines starting with '## /' are treated as
+    disabled exports — everything else that starts with '#' is a plain comment
+    and is left untouched."""
     entries = []
     try:
         with open('/etc/exports', 'r') as f:
@@ -152,14 +157,14 @@ def _parse_exports():
                 if not stripped:
                     entries.append({'kind': 'blank', 'raw': raw})
                     continue
+                if stripped.startswith(_DISABLED_PREFIX + '/'):
+                    inner = stripped[len(_DISABLED_PREFIX):]
+                    parts = inner.split(None, 1)
+                    entries.append({'kind': 'export', 'enabled': False,
+                                    'path': parts[0], 'rest': parts[1] if len(parts) > 1 else ''})
+                    continue
                 if stripped.startswith('#'):
-                    inner = stripped[1:].strip()
-                    if inner.startswith('/'):
-                        parts = inner.split(None, 1)
-                        entries.append({'kind': 'export', 'enabled': False,
-                                        'path': parts[0], 'rest': parts[1] if len(parts) > 1 else ''})
-                    else:
-                        entries.append({'kind': 'comment', 'raw': raw})
+                    entries.append({'kind': 'comment', 'raw': raw})
                     continue
                 parts = stripped.split(None, 1)
                 entries.append({'kind': 'export', 'enabled': True,
@@ -173,7 +178,7 @@ def _write_exports(entries):
     with open('/etc/exports', 'w') as f:
         for e in entries:
             if e['kind'] == 'export':
-                prefix = '' if e['enabled'] else '#'
+                prefix = '' if e['enabled'] else _DISABLED_PREFIX
                 rest = f'\t{e["rest"]}' if e['rest'] else ''
                 f.write(f'{prefix}{e["path"]}{rest}\n')
             else: