Fix bridge recovery deadlock after terminal removal

[ClaudiuSchuster]

What changed

• Allow the independent Proton bridge guard to recover after two separated,
  path-correlated block-upload 502 cycles only when a terminal remote-removal
  response follows at or after the newest cycle.
• Preserve the existing safe-version, connectivity, bandwidth, activity,
  generation, queue, Dirty-cache, cooldown and restart-budget guards.
• Report a fresh terminal recovery stall as Attention instead of Ready
  when the protected queue has no payload speed and no process-owned TCP
  connection.
• Document the narrow two-cycle terminal signature and its conservative
  negative cases.

This closes a state-machine deadlock where a removed remote draft could leave
the block worker unable to emit the third failure cycle required by the normal
bridge path.

Fixes #37

Safety impact

• Credentials and authentication state are unchanged.
• The RC endpoint remains owner-local and is only read for the existing guarded
  observations and validation.
• A restart is still possible only after two separated idle probes and every
  existing generation-bound safety check succeeds.
• Dirty VFS data, metadata namespaces and remote files are never deleted or
  moved by this change.
• No privileged setup behavior changes.

Verification

• make verify
• Behavior-specific positive and negative recovery fixtures were added.
• UI changes were exercised in English and German, at minimum width and in
  both idle and active fixtures on an isolated GTK Broadway display.
• No real credentials, tokens, private paths or personal filenames appear
  in code, fixtures, logs or screenshots.
• The protected queue survived the controlled recovery and demonstrated
  renewed payload and process-network progress afterward.
• User-facing Operations and Troubleshooting documentation is updated;
  version metadata is intentionally unchanged for this unreleased branch.
• Super-Linter 8.7.0 passed locally, including Ruff format, ShellCheck,
  Gitleaks, Zizmor, Markdown/Prettier and YAML/Prettier.