fix: critical bugs in agent identity provisioning [#442]

Email domain bug (would have caused all provisioning to fail):
- Cloudron email default was tsys-cloudron.knel.net (the dashboard host)
  instead of turnsys.com (the actual identity domain). Fixed in 3 places.
- Added explicit cloudron_email field to all agents in agents.yaml.example.

Other fixes:
- STATE_DIR.mkdir() moved from module level to main() so --dry-run and
  --help work outside the container.
- IndexError guard: password_inputs[0] crashes if zero fields found.
- State file save moved to finally block so partial results survive
  provisioning failures.
- Exception in provision_agent no longer re-raised (was preventing state
  file write and summary reporting).
- BW item_exists no longer swallows network/session errors as 'not found'
  (was causing duplicate credential creation).
- Redundant -u flag in bw generate (-uluns → -ulns).
- Dockerfile: npx install with || true → npm install -g (silent failure
  would cause runtime 'bw: command not found').
- Added .dockerignore to prevent .env/agents.yaml/state from entering image.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

Dockerfile

@@ -9,7 +9,7 @@ RUN apt-get update && \
     && rm -rf /var/lib/apt/lists/*
 
 # Install Bitwarden CLI
-RUN npx -y @bitwarden/cli@2026.7.0 || true
+RUN npm install -g @bitwarden/cli@2025.6.0
 
 # Install Python dependencies
 COPY requirements.txt /tmp/