Activate login account view and event vocabulary

[shiny-code-bot]

Finish Line

The dormant login account view, its snapshots, and its event vocabulary compile and are reachable through internal TUI entry points without starting login side effects.

Current Status

PR #699 is open from commit 3ff19d154e. The dormant login-account view now compiles; all 30 focused tests and eight existing snapshots pass unchanged. Internal account-list/add-account navigation is wired, while backend login/switch/remove events intentionally remain warning-only and unreachable until #695-#698. Exact Bazel Clippy clears the three account-label diagnostics; the 14 remaining diagnostics are assigned to #695/#696.

Acceptance Criteria

• Declare and export the login account view module.
• Restore active_login_add_account_id through BottomPaneView, BottomPane, and ChatWidget.
• Restore redacted SecretApiKey, account-selection payload types, and the nine login/account event variants.
• Add exhaustive event-dispatch arms that make view navigation functional without starting backend login operations.
• Reactivate the existing login-account tests and snapshots unchanged.
• Exact Bazel Clippy clears the account-label reachability diagnostics without broad allowances.

Relationships

• First implementation stage of Restore login account management TUI wiring #690.
• Blocks direct-store login flow restoration.

Open Questions

• None; backend side effects remain intentionally deferred to the next child.