polish: rebrand to Fleet Ops, add trilingual i18n, adaptive demo guide, and UX overhaul

Rebrands the product from MobilityOps to Fleet Ops across the UI, backend defaults and
knowledge base, and makes nl-BE/en-GB/fr-BE full first-class languages: i18next with
eager-bundled per-namespace resources, a persisted accessible language switcher (topbar
and mobile drawer), locale-aware date/number formatting, and a coverage test that fails
the build on any missing or empty translation key.

Backend dynamic content (demo scenarios, blocked-reason text, integration status) moves
from fixed English/Dutch prose to stable message codes + params so the frontend can
localize it; the demo knowledge base gains a fully translated NL/EN/FR procedure corpus
(11 documents each) with per-language retrieval and localized evidence-state messages.

The Demo Guide becomes breakpoint-adaptive: a docked rail on extra-wide desktop, a
floating panel that auto-collapses to a persistent, closable progress chip on standard
desktop/tablet, and a collapsed/half/full bottom sheet on mobile -- with scroll+focus+
highlight on "go to this step", Escape handling, and reduced-motion support.

The Data Quality Workbench gets accessible choice-card decisions with a clear primary/
secondary/tertiary action hierarchy; the Automation ledger groups repeated successes and
uses meaningful short refs; the Audit trail groups events by correlation id with human
action labels and readable before/after diffs. Attention Queue, Today's movements,
Vehicles, Bookings and Data Quality rows are fully clickable (stretched-link pattern)
with independent secondary links, keyboard support and mobile touch targets.

Fixes a topbar overflow on mobile caused by the new language switcher (moved into the
mobile drawer at <=960px) and two dangling aria-labelledby references introduced this
session. Updates all affected Playwright specs for the new nl-BE default and the new
Audit/DemoGuide DOM structure, and adds new i18n-coverage, demo-guide-adaptive and
clickable-rows specs. 131 backend tests, Ruff and mypy, and 71 Playwright tests pass.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/i18n/locales/en-GB/auth.json

@@ -0,0 +1,23 @@
+{
+  "brandTagline": "Control Centre",
+  "orgLine": "Demo organisation: {{orgName}} (fictional)",
+  "headline1": "Every hand-off.",
+  "headline2": "One clear view.",
+  "defaultDescription": "Fleet Ops brings vehicle, booking and operational data together, supports rental processes, detects data-quality problems and automates controlled follow-up steps.",
+  "footnote": "Synthetic demo · no real customer or vehicle data · resettable at any time",
+  "accessEyebrow": "Demo access",
+  "accessHeading": "Choose how to start",
+  "accessIntro": "No password needed. Each role opens a scoped synthetic environment — all workflows and controls are really implemented.",
+  "startGuidedDemo": "Start guided demo",
+  "exploreAsOperationsManager": "Explore as Operations Manager",
+  "exploreAsOperationsManagerDetail": "Full overview, quality resolution and retries",
+  "exploreAsRentalEmployee": "Explore as Rental Employee",
+  "exploreAsRentalEmployeeDetail": "Bookings, returns, fleet and procedures",
+  "safeByDesignTitle": "Safe by design",
+  "safeByDesignDetail": "Every action is logged and is resettable in this demo.",
+  "loginFailed": "The demo session could not be started. The API may be unreachable.",
+  "roleOperationsManager": "Operations manager",
+  "roleRentalEmployee": "Rental employee",
+  "switchRole": "Switch role",
+  "logout": "Log out"
+}