Add venv self-bootstrap to the remaining agent-callable scripts

ga4-site-provision.py re-execs itself under websites-tools/venv so any agent can run 'python3 <abs-path> <args>' from any cwd with no activation. The other scripts in websites-tools/scripts/ still require 'cd websites-tools && source venv/bin/activate' first, which makes them procedures rather than callable tools. Apply the same 4-line preamble (from config import PYTHON_BIN; if sys.prefix == sys.base_prefix: os.execv(...)). Trap: do NOT compare interpreter paths - venv/bin/python3 is a symlink to the system interpreter so resolve() collapses both sides and the re-exec never fires; use sys.prefix == sys.base_prefix. Priority targets are the ones other agents call: seo-run-all.py, gsc_report_generator.py, ga4_report_generator.py, check-seo-status.py, project-info.py.