Add account-synced personal vehicles and parked-location state

[Medformatik]

Problem

Vehicle-dependent routing, EV planning, route cost/emissions, parking, and arrival handoff need a reusable personal vehicle model. Today users can configure only a single local EV-like profile and cannot retain a small garage or a deliberate parked position across clients.

Current state

• EV planning has built-in presets and one custom vehicle stored in local settings.
• There is no account-synced multi-vehicle entity, default vehicle, combustion/hybrid profile, or parked-location record.
• Navigation arrival and park-and-ride exist, but neither writes personal parked state.

Proposed solution

Add an account-scoped vehicle garage plus privacy-minimized parked state. Reuse one canonical vehicle contract across EV range, route impact/cost, routing options, parking, and arrival UI. Keep anonymous/local use possible.

Acceptance criteria

• Users can create, edit, archive/delete, and choose a default from multiple vehicles.
• The contract supports EV, combustion, hybrid, motorcycle, and bicycle-relevant parameters with units and validation.
• Built-in presets can initialize a personal profile without becoming mutable global records.
• Vehicle data syncs for signed-in users while anonymous users retain a local-only equivalent.
• Routing/EV/cost consumers receive a deliberate selected vehicle rather than reading unrelated UI settings.
• Users can manually save, update, navigate to, and clear a parked position.
• Arrival may offer to save the current/vehicle position, but does not silently build location history.
• Parked state stores one current record per vehicle (position, time, optional note/source) with explicit retention.
• Location/vehicle data is encrypted at rest under the documented trust model and excluded from logs/analytics.
• Export/account deletion removes vehicles and parked state; shared links never expose them implicitly.
• Offline edits and cross-device conflicts have a deterministic policy.
• Tests cover units, migration from the current custom EV setting, authorization, privacy, and deletion.

Alternatives considered

Keeping separate vehicle settings in every feature creates drift. A full automatic parking-history tracker collects more sensitive data than the current use cases need.

Area

Accounts, routing, EV planning, parking, navigation, settings.

Dependencies

Coordinate parked-location trust decisions with the E2EE/trust-model issue (#312). Arrival integration is tracked in #309.