Initial commit: ImpactFlow Discovery + Google OAuth auth layer

Discovery service (pre-existing): FastAPI + async SQLAlchemy + Alembic +
SQLite + Anthropic, with a five-prompt static UI that produces an Enneagram
+ Ikigai profile.

Auth implementation (this change set) follows
Impact_Flow_Auth_Plan_OAuth.html, adapted to the discovery_conversation /
discovery_profile schema:

- app/auth.py: Google OAuth registration, JWT issue/decode, dual-auth
  dependency (Bearer JWT or X-API-Key), refresh-token hashing, domain
  allow-list, synthetic api-key-admin user
- app/tracking.py: ActivityTrackingMiddleware + log_activity helper;
  tags machine-to-machine calls source=mcp
- app/routers/auth.py: /api/auth/{login,callback,refresh,logout},
  /api/me, /api/me/{stats,sessions,sessions/{id}}
- app/routers/activity.py: /api/activity, /api/activity/summary,
  /api/admin/activity, plus prune_old_activity (90-day retention)
- app/routers/discovery.py: every route now user-scoped via the auth
  dependency; /discovery/profile/{user_id} -> /discovery/profile/me
- alembic/versions/002_add_auth.py: users, refresh_tokens, activity_log
- tests/test_auth.py: 8 tests covering 401 paths, X-API-Key admin
  resolution, JWT round-trip, admin gating, domain allow-list
- README.md: Authentication section, expanded env-var table, updated
  data-model and API-reference tables
- .env.example: new GOOGLE_*, JWT_*, IMPACTFLOW_API_KEY, CORS_*,
  ALLOWED_EMAIL_DOMAINS placeholders
- .gitignore: also exclude data/*.log

Tests: 19/19 pass (11 pre-existing + 8 new). smoke_test.py exercises the
full discovery flow under X-API-Key plus 401 paths, OAuth login redirect,
activity logging, and /api/me/stats.

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

alembic.ini

@@ -0,0 +1,42 @@
+# Alembic configuration for the ImpactFlow self-discovery module.
+# The actual sqlalchemy.url is resolved from the DATABASE_URL env var in
+# alembic/env.py (the async "+aiosqlite" driver is stripped for migrations).
+
+[alembic]
+script_location = alembic
+prepend_sys_path = .
+sqlalchemy.url = sqlite:///./data/discovery.db
+
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARNING
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARNING
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S