Refine edge-to-edge map search controls

[SebastianBoehler]

Summary

• expands the map view out of the centered app content box so it reaches edge-to-edge
• widens the bottom search control by using the full map overlay width
• changes Ask AI into an icon-only round button inside the search field suffix
• shows the AI action only while the search field is focused
• disables map rotation gestures so the map stays oriented more predictably

Stacking

This PR is stacked on #25 and contains the follow-up refinement feedback only. Merge #25 first, then this PR can be retargeted to main or merged after the base branch is available.

Verification

• /tmp/studyos-tools/flutter/bin/flutter analyze
• /tmp/studyos-tools/flutter/bin/flutter test test/maps_controls_test.dart test/navigation_test.dart test/map_location_models_test.dart
• /tmp/studyos-tools/flutter/bin/flutter test

[SebastianBoehler]

Reviewed the stacked follow-up diff. Intent looks clear: keep the map full-width, widen the bottom overlay, move the assistant affordance into the search suffix, hide it until search focus, and disable map rotation.

No blocking code findings from the stacked diff. The main risk areas I checked were scaffold/layout regressions from letting only AppView.maps escape the 760px content constraint, focus-driven visibility for the Ask AI action, and whether map controls still expose search/open/assistant actions through tests.

Verification run locally from the PR head:

• /tmp/studyos-tools/flutter/bin/flutter analyze
• /tmp/studyos-tools/flutter/bin/flutter test test/maps_controls_test.dart test/navigation_test.dart test/map_location_models_test.dart
• /tmp/studyos-tools/flutter/bin/flutter test

Smallest useful next action: since #25 is now merged, retarget this PR from issue-24-map-assistant-ui to main, then wait for the pending Flutter CI check to finish before a human merges.