feat(app): add maps navigation page

[SebastianBoehler]

Summary

• Adds a new Maps page backed by flutter_map / OpenStreetMap tiles and a Nominatim search client for Tuebingen destinations.
• Wires the page into the app navigation and home shortcuts.
• Adds selected-location actions to ask StudyOS with structured location context or open the destination in an external maps app.
• Adds map location parsing/prompt tests and navigation coverage.

Notes

• The MVP intentionally avoids current-location permissions and turn-by-turn routing. External maps handles navigation fallback for now.
• OSM/Nominatim attribution is shown in the UI. If this grows beyond a course prototype, we should revisit tile/geocoding provider policy and rate limits.

Verification

• dart format --output=none --set-exit-if-changed lib test
• flutter analyze
• flutter test
• Android APK build was not run locally because this runtime does not have an Android SDK configured; GitHub Actions installs the SDK and will verify debug/release APK builds.

Closes #22

[SebastianBoehler]

Reviewed the PR for the new Maps page. I do not see a blocking code issue from the diff: the feature is scoped to the Flutter app, avoids current-location permissions, keeps selected-location context explicit before handing it to the assistant, and adds basic parsing/navigation coverage.

Likely risk areas to keep in view before merge:

• OSM/Nominatim dependency behavior: the PR uses the public OSM tile server and public Nominatim search. The implementation sets a tile user-agent package name and a Nominatim User-Agent, and the UI shows attribution. That matches the important prototype-level requirements, but the public policies still cap Nominatim usage at about 1 request/second and expect identifiable clients, so this should stay button-triggered and low-volume. If Maps becomes a core feature, move to a dedicated provider or hosted/local geocoder path.
• Manual runtime checks: CI is still pending as of this review, and this runtime does not have flutter/dart installed, so I could not rerun dart format, flutter analyze, or flutter test locally. A human should wait for GitHub Actions and smoke-test map tiles/search/external map launch on the target platform.
• UX failure paths: search failures are displayed, but external map launch failure currently throws. That is probably acceptable for an MVP, but a snackbar/status message would be a small follow-up if this path proves flaky.

Smallest useful next step: wait for the Flutter CI result, then do one manual smoke test of: open Map tab, search a Tuebingen destination, select a result, click “Ask StudyOS”, and click external maps. If CI passes and that smoke test works, this looks ready for human review/merge consideration.

[MertOkur]

lgtm