Feature/corrected coords consolidation

[nagisml]

related to #936 ping me if a rebranch will be needed after the other PR's

Corrected coordinates: consolidate entry points, add distance/bearing and clear button

Corrected coordinates can be set from the detail panel, the cache table menu, the map menu and the Edit Cache dialog. Each entry point had its own database-write code and refreshed the UI differently, which led to stale views and dialogs that looked different.

Changes

• One shared DB write: the new set_corrected_coords() in db/corrected_coords.py is used by the detail panel, the table menu and the map menu.
• Same dialog everywhere: opened from the detail panel, the dialog now also shows the original coordinates.
• Consistent refresh: _on_corrected_coords_changed now also refreshes the detail panel when it shows the affected cache. Previously it stayed stale after a table or map change.
• No double reload: the table no longer reloads the row itself; the signal handler does it once.
• New: distance and bearing from the original to the corrected coordinates, updated live in the dialog. It follows the miles/km and haversine/vincenty settings and is translated into all 11 languages.
• New: "Clear corrected coordinates" button in the dialog, shown only when corrected coordinates already exist.

Tests

New unit and e2e tests cover the shared DB write, detail-panel refresh from the table and the map, the distance/bearing line and the clear button. The full unit and e2e suites pass.