feat: mută secretele Discord/Telegram din TOML în .env

TOML-urile din configs/ rămân 100% calibrare — safe to commit. Secretele
(ATM_DISCORD_URL, ATM_TG_TOKEN, ATM_TG_CHAT) trăiesc în .env la rădăcină
(ignored), cu loader stdlib (shell wins peste file). Validare fail-fast
pentru env lipsă, placeholder REPLACE_ME, chat_id non-numeric.

Include .env.example + secţiune README §Secrets. Tests: 19 noi (env loader +
missing-env + placeholder + chat_id + regression post-migrate snapshot).

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

CLAUDE.md

@@ -7,13 +7,14 @@ Personal Faza-1 tool for the M2D strategy. Python 3.11+.
 ```bash
 pip install -e ".[windows]"    # Windows: live capture
 pip install -e ".[dev]"        # Linux/macOS: dev + tests (WSL: create venv first)
+cp .env.example .env           # secretele Discord/Telegram (vezi README §Secrets)
 atm calibrate                  # Tk wizard
 atm debug --delay 5            # one-shot capture + detect
 atm validate-calibration calibration/calibration_labels.json   # offline color gate
 atm run --start-at 16:30 --stop-at 23:00                   # live session
 atm run --tz America/New_York --oh-start 09:30 --oh-stop 16:00  # NYSE window override
 atm dryrun samples             # corpus gate
-pytest -q                      # 192 tests (184 core + 8 scenarii regresie)
+pytest -q                      # 210+ tests (core + 8 scenarii regresie + env loader)
 pytest tests/test_scenarios_regression.py -v    # FSM pe imagini reale
 ```