Let a placed handover be moved before the rest are placed

[aquasolterra]

When a recording is imported across several entries, the screen asks for each handover in turn. Until now every tap placed the next open handover, so a badly placed one could only be corrected after all the others were placed, and then only through "move the nearest", which could pick its neighbour.

Change

One rule throughout: a tap on the map places the selected handover.

• A row of numbered chips under the map ("Handover 1", "Handover 2", …) shows which handover is selected and whether each is placed; tapping a chip selects it.
• The marks on the map are numbered, and the selected one is drawn larger.
• After a tap the selection advances to the next open handover; once none is open it stays put, so another tap refines the one just placed.
• The "nearest" rule is gone.
• Snapping keeps a handover between the nearest placed handovers on either side (not just its immediate neighbours), since with a free selection the adjacent one may still be open.
• Side fix: with nothing to ask (a single leg), the summary line is no longer printed twice.

The selection lives in the panel, not on the map: tappable marks were tried before and lose the gesture arena to flutter_map's own onTap.

Tests

Two new widget tests in test/track_import_screen_test.dart: moving handover 1 while handover 2 is still open, and refining the last placed handover after all are placed. flutter analyze is clean; the full suite passes. Not yet tried on a device.

Docs: AGENTS.md, docs/features.md, CHANGELOG.md.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 97.95918% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...features/map/presentation/track_import_screen.dart	97.95%	1 Missing ⚠️

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