feat: add authenticated Wayfarer routing

[stef-k]

Summary

• add authenticated, provider-neutral routing through the configured Wayfarer server
• discover eligible server-owned transport profiles and fence chooser, capability, route execution, and final publication with the backend identities from Expose provider-neutral Mobile routing profile discovery Wayfarer#528
• preserve saved Segment geometry as highest authority and retain explicit straight-line Direct guidance for unavailable, cancelled, stale, or invalid hosted routing
• keep hosted routes, profile choices, attribution, and provenance transient; durable reuse remains owned by Add bounded offline Wayfarer route persistence and reuse #261

Closes #260.

Product behavior

• Mobile contacts only authenticated Wayfarer routing endpoints; provider credentials remain server-side
• exact Segment profile IDs and bounded ad-hoc profile choice are supported without deriving identity from labels
• stale catalog choices, selected authority drift, session/server/target/location/profile changes, Direct selection, cancellation, and replacement fail locally without publishing an obsolete route
• linked attribution and safe hosted provenance exist only with the active hosted route
• old or routing-disabled backends preserve Trip use, synchronization, saved geometry, and Direct guidance

Validation

• focused hosted routing and publication tests: 44 passed
• hosted/navigation/settings/synchronization selection: 664 passed
• complete Release suite: 1,943 passed, 0 failed, 0 skipped
• Android Release compilation: succeeded with 0 errors; existing AndroidX/XAML warnings remain
• git diff --check: passed
• Code Guard: complete except for the explicitly approved unchanged ApiClient.cs legacy-size exception at blob 575237dc5173eaede030d7a10742ab8df413bee7 and 1,165 counted LOC

Screenshots

Not applicable: this change uses the existing profile-choice dialog and navigation HUD rather than adding a new screen or layout.

Database and deployment

• no schema change or migration
• no route/profile persistence, cache, preference, SecureStorage, or file storage
• no deployment, installation, or publication is included in this PR

Backend dependency

Consumes the additive routing profile discovery and selected-authority contract merged in stef-k/Wayfarer#529. New Mobile treats an old backend without discovery as routing unavailable.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
WayfarerMobile.Core	88%	80%	995	✔
Summary	88% (1397 / 1593)	80% (689 / 866)	995	✔