Repo is the install location; all scripts self-locate

Users now clone to a persistent ZFS pool and the repo stays in place.
No files are copied on install — the PREINIT hook points directly into
the clone. Scripts derive PATCH_DIR from their own path at runtime.

- install.sh: PATCH_DIR=$(dirname $0); register patch/apply.sh as
  PREINIT target; chmod only, no cp; update pipe-install error message
- patch/apply.sh: PATCH_DIR=$(dirname $0)/..; substitute PATCH_DIR
  into sitecustomize.py via sed when writing to site-packages;
  reference patch_ui.py as patch/patch_ui.py
- recover.sh, uninstall.sh: PATCH_DIR=$(dirname $0)
- uninstall.sh: look for patch/apply.sh in PREINIT registry
- patch/create_task.py: _PATCH_DIR derived from __file__; apply.log
  path in error message derived from _PATCH_DIR
- patch/sitecustomize.py: /data/truecloud-patch remains as placeholder
  substituted by apply.sh on each install
- .gitignore: exclude runtime files (apply.log, hook_status.json, disabled)
- README: document clone-to-pool install; update all example paths

patch/create_task.py

@@ -48,7 +48,8 @@ import sys
 import urllib.error
 import urllib.request
 
-_STATUS_FILE = "/data/truecloud-patch/hook_status.json"
+_PATCH_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+_STATUS_FILE = os.path.join(_PATCH_DIR, "hook_status.json")
 
 
 def make_client(host, api_key, insecure=False):
@@ -117,7 +118,7 @@ def cmd_verify():
         print("All patches installed. Run a test backup to confirm end-to-end.")
     else:
         print("One or more patches failed to apply.")
-        print("Check /data/truecloud-patch/apply.log and journalctl -u middlewared")
+        print(f"Check {os.path.join(_PATCH_DIR, 'apply.log')} and journalctl -u middlewared")
         sys.exit(1)
 
 def cmd_list_credentials(client, _args):