Rename the service to BugTrail ...

Bug + trail: the recorded trail of actions leading to the bug.
User-facing rename in the web panel shell, extension manifest/popup/
options, API title, i18n locales and README; Firefox id is now
bugtrail@gnexus.space. Internal @ltt/* package scopes unchanged.

Co-Authored-By: Claude Code <noreply@anthropic.com>

Server: FastAPI backend with auth, projects, reports, uploads ...

- FastAPI + SQLAlchemy async + Alembic, PostgreSQL in docker-compose
- Auth: argon2id, cookie sessions (web) + bearer tokens (extension)
- Unguessable share tokens (128-bit) on projects and reports
- Content-addressed file storage with mime sniffing, token-scoped download
- Reports with nested steps; server-side password masking

Co-Authored-By: Claude Code <noreply@anthropic.com>