feat(tui): redesign shell, fix scrolling, auth and daemon polling

[solisoft]

The TUI gets a left sidebar, a mint-on-ink palette (src/tui/theme.rs), mouse support and a redrawn dashboard. Review follow-ups folded in:

Correctness

• Login: q was bound to quit under an if password.is_empty() guard that applied to the whole or-pattern, making every password starting with q unenterable. Quit is now Esc-on-empty (plus Ctrl+C/Ctrl+D).
• G set scroll_offset to the last index; every screen renders .skip(scroll_offset), so it collapsed the list to a single row. Added max_offset(len, visible) — the top of the last page — and a clamp pass on render so a resize or a shrinking list cannot strand the viewport.
• Routes counted unfiltered rules for selection bounds while rendering the filtered list, and resolved the cursor back to a rule with a different predicate (matcher Debug vs format_matcher) than the one it displayed — a search could line a row up with a rule other than the one d deleted. Both now share screens::routes::filter_indices.
• Config screen could not scroll at all: get_max_selection returned 0, so move_selection bailed. Added a text-viewport scroll path and cached the file contents instead of re-reading them every frame.
• tail_file used read_to_string, so a seek landing mid-codepoint (or any non-UTF-8 byte) blanked the log viewer with no explanation. Reads bytes and converts lossily; open/read errors now name the path and cause.

Responsiveness

• Daemon metrics moved off the render thread into a background poller. The inline block_on froze the UI for the request timeout every tick, worst exactly when the daemon was down. The client is built once, not per tick.
• Mouse reporting uses ?1000/?1006 rather than crossterm's EnableMouseCapture, which also enables ?1003 any-motion tracking: a redraw per pointer movement, and terminal text selection taken away from the user (the OSC-52 fallback).
• The event loop only repaints when something changed.

Reporting

• daemon_ok: bool -> DaemonStatus. A proxy running with admin.enabled = false is healthy; it was reported as "daemon down". Metric panes now show why they are empty instead of a confident 0.
• Dashboard regained listen/https/tls/admin/auth/scripts, in-flight, bytes in/out, TLS connections, half-open circuits and the apps overflow hint.

Docs

• docs/tui-screenshots depicted a UI that was never built (top tabs, cyan palette, panels since removed). Regenerated against the shipped layout, with a README stating they are mockups and where each element's source of truth lives.