Adopt shared-SA model, add DEPLOY guide, MIT license

- Install flow now assumes one admin-distributed service account JSON shared
  across the team. Each user creates their own Google Sheet and shares it
  with the SA email; per-user GCP project setup is gone.
- DEPLOY.md: a step-by-step walkthrough for non-technical users following
  along with an AI agent (Terminal basics, screenshots-worth of expected
  output, common-error table).
- scripts/append_row.py: sheet_id field accepts either a bare ID or a full
  Google Sheets URL; normalize_sheet_id() extracts the ID via regex.
- scripts/setup.md: rewritten as an admin guide (one-time GCP setup, key
  rotation) plus a troubleshooting reference.
- LICENSE: MIT (previously "private — internal use"). README license
  sections updated to match.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

SKILL.md

@@ -13,7 +13,7 @@ Default working language: **English**. All written output (row values, replies)
 - Caption may be empty, or may add context (who paid, split %, category hint, payment method). Always incorporate caption if present.
 
 ## Prerequisites (check once per session)
-1. `~/.openclaw/workspace/skills/AutoACCT/config.json` exists. If only `config.example.json` is present, **stop** and tell the user to copy it and fill in `sheet_id`, `worksheet`, `service_account_path`. Point them at `scripts/setup.md`.
+1. `~/.openclaw/workspace/skills/AutoACCT/config.json` exists. If only `config.example.json` is present, **stop** and tell the user to copy it and fill in `sheet_id`, `worksheet`, `service_account_path`. Point them at the README install section.
 2. Python deps installed: `google-api-python-client`, `google-auth`. If `append_row.py` fails with ImportError, instruct the user to run `pip install google-api-python-client google-auth` and retry.
 
 ## Workflow