- Add _parse_range() helper: validates Range header bounds, raises 416 on invalid
- Add stream_document_content endpoint with get_regular_user dep (admin → 403)
- Access check: owner OR Share.recipient_id; neither → 404
- Bytes fetched via get_object() only — presigned_get_url() never called
- Range requests return 206 + Content-Range header
- Add pdf_open_mode column to User ORM model (migration 0004 already applied)
- Use HTTP_416_RANGE_NOT_SATISFIABLE (non-deprecated constant)
- Add BackupCode model to db/models.py with user_id FK, code_hash (Argon2), used_at (nullable)
- Add ix_backup_codes_user_id index on backup_codes.user_id
- Add password_must_change BOOLEAN NOT NULL DEFAULT false to User model (ADMIN-01)
- Extend config.py Settings with JWT, SMTP, admin bootstrap, and CORS fields (D-01, D-04, D-09)
- Add env_list_separator=',' for cors_origins env var parsing
- Append PyJWT, pwdlib[argon2], pyotp, aioredis, slowapi to requirements.txt
- Add .env.example entries for SECRET_KEY, ADMIN_EMAIL, SMTP_*, CORS_ORIGINS
- Create migration 0002 adding backup_codes table and password_must_change column
- Add TDD tests for all Task 1 acceptance criteria (7 tests pass)