Fix six quality findings from code review

sitecustomize.py:
- Restore _record_status count barrier: write the status file only after all
  patches have reported. middlewared.plugins.cloud_backup.restic is imported
  lazily (only when a backup task runs), so without this barrier verify would
  declare "all patches active" based solely on the B2 patch that fires at
  startup. Barrier now gates on _Finder._targets rather than the removed
  _PATCHES dict.
- Add comment in exec_module noting the if/elif must stay in sync with
  _Finder._targets, making the coupling visible.

patch_ui.py:
- Merge find_webui into find_bundle: previously find_bundle(None) would crash
  with os.walk(None) if main()'s guard were removed. Merged function returns
  a 3-tuple (webui_dir, path, content); webui_dir=None means no candidate
  directory found, path=None means directory found but pattern absent.
  main() still produces distinct messages for each failure mode.

create_task.py:
- Split triple-chained .get() in cmd_list_tasks into two lines; the or {}
  handling for None credentials was buried inside a one-liner.

uninstall.sh:
- Fix find loop: replace "for x in $(find ...)" with "while IFS= read -r"
  to handle paths containing spaces or newlines.
- Add #!/usr/bin/env shebang form to Python detection, matching apply.sh.
  Without this, uninstall on a system where middlewared uses the env form
  would silently leave sitecustomize.py in the wrong site-packages.

patch/sitecustomize.py

@@ -105,6 +105,7 @@ class _Loader:
             self._finder._mark_done(fullname)
 
         # exec_module succeeded — apply our patch.
+        # Must stay in sync with _Finder._targets.
         try:
             if fullname == "middlewared.rclone.remote.b2":
                 _patch_b2(module)
@@ -187,6 +188,8 @@ def _record_status(fullname: str, ok: bool, detail: str = "") -> None:
     if fullname in _hook_status:
         return  # idempotent: first call wins
     _hook_status[fullname] = {"ok": ok, "detail": detail}
+    if len(_hook_status) < len(_Finder._targets):
+        return  # wait until all patches have reported before writing
 
     payload = {
         "patched_at": time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime()),