feat(dashboard): log navigation — range presets, date jumps, and search for both security logs

[VijitSingh97]

Closes #823 — the Security view's two log tables were navigable only by scrolling (and the config-change card's lone grouping dropdown).

What

Both panels gain one shared control row: the chart's range presets (24 Hr / 1 Wk / 1 Mo / All) for following a live log, two native date inputs for jumping to a specific day or span (the "to" date covers its whole day via a half-open next-midnight bound), and a debounced search box matching any field. Filters compose; the existing hour/day/month grouping still applies on top.

Filtering is server-side (?from&to&q on /api/access and /api/audit) so a match deeper than the glance tail is found: one filter_log_entries helper serves both surfaces by normalizing each entry's ts (epoch on access rows, canonical UTC ISO on audit rows) onto one epoch axis — an undatable row matches no time window but still matches a pure text search. Malformed bounds read as absent (a bad query never 500s a log view); q is trimmed, length-capped, and only ever compared — the existing sanitation path is untouched. The access read deepens to a bounded 1000-row tail only while filtering; the failed-login counters always describe the whole tail. Filtered views lift the 20-row glance cap and report an honest "No entries match this filter".

Verified live (harness)

Preset click narrows to the window and lifts the cap; search composes with the active range — including the honest empty intersection when the searched entry sits outside it; the audit card filters independently; controls render in both cards with the active preset marked.

Coverage

• test_audit_service.py: the filter helper — half-open window across both ts shapes on one axis, undatable-row semantics, case-insensitive any-field search incl. numeric values, composition, non-string/non-number ts.
• test_server.py: both routes' param handling — window + search + whole-tail counters + malformed-bounds degradation.
• securityview.test.mjs: buildLogQuery (presets, date-override, next-midnight bound, URL encoding), controls rendering with active-preset marking, cap-lift under filter vs glance cap, honest empty messages.
• Dashboard 1649 pass / 96.9% total / patch 100%; frontend suite green; make lint clean; docs updated in docs/dashboard.md.

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