Resolve /usr/local/CyberPanel/bin/python on install, upgrade, downgrade

Install:
- install.py: in preFlightsChecks.call(), replace missing CyberPanel python
  with /usr/bin/python3 and force shell=True so any code path (including
  old/cached script) never hits FileNotFoundError.

Upgrade:
- cyberpanel_upgrade.sh: resolve CP_PYTHON (CyberPanel, CyberCP, python3)
  before running upgrade.py and configure.py; use it for both.
- plogical/upgrade.py: add _python_for_manage(), use it in GeneralMigrations,
  collectstatic, and upgradePip so migrations/collectstatic work when
  /usr/local/CyberPanel/bin/python is missing.

install/install.py

@@ -2839,6 +2839,13 @@ module cyberpanel_ols {
     # Using shared function from install_utils
     @staticmethod
     def call(command, distro, bracket, message, log=0, do_exit=0, code=os.EX_OK, shell=False):
+        # Fix missing /usr/local/CyberPanel/bin/python on install/upgrade (avoid FileNotFoundError)
+        if isinstance(command, str) and '/usr/local/CyberPanel/bin/python' in command:
+            if not os.path.isfile('/usr/local/CyberPanel/bin/python'):
+                fallback = '/usr/bin/python3' if os.path.isfile('/usr/bin/python3') else '/usr/local/bin/python3'
+                if os.path.isfile(fallback):
+                    command = command.replace('/usr/local/CyberPanel/bin/python', fallback, 1)
+                    shell = True
         return install_utils.call(command, distro, bracket, message, log, do_exit, code, shell)
 
     def checkIfSeLinuxDisabled(self):