refactor: migrate to Navigation 3 with connected composable overloads

[mtrewartha]

Summary

• Migrates from the previous navigation setup to Navigation 3 (NavDisplay, NavKey, entryProvider)
• Introduces "connected" composable overloads in each feature module (LocationView, CompassView, SunView, SettingsView) that internally create their ViewModel, collect state, and provide CompositionLocals — decoupling the app module from feature internals
• Moves the coordinatesFormatter helper from MainView into the location module as rememberCoordinatesFormatter in the locals package, where it belongs alongside LocalCoordinatesFormatter
• Simplifies MainView.kt so each nav entry only passes navigation callbacks and app-level concerns (sharing intents, license/privacy URLs)
• Extracts nav entry definitions into focused extension functions (locationEntries, compassEntries, sunEntries, settingsEntries)

Test plan

• ./gradlew assembleDebug — compiles successfully
• ./gradlew test — all tests pass
• Manual: navigate between all 4 tabs, open each help screen, share coordinates, change settings, verify theme switching works

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 0% with 190 lines in your changes missing coverage. Please review.
✅ Project coverage is 16.81%. Comparing base (c4d67c9) to head (ea692cd).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
.../src/main/java/io/trewartha/positional/MainView.kt	0.00%	101 Missing ⚠️
...o/trewartha/positional/location/ui/LocationView.kt	0.00%	28 Missing ⚠️
...o/trewartha/positional/settings/ui/SettingsView.kt	0.00%	25 Missing ⚠️
.../io/trewartha/positional/compass/ui/CompassView.kt	0.00%	13 Missing ⚠️
...n/kotlin/io/trewartha/positional/sun/ui/SunView.kt	0.00%	11 Missing ⚠️
...o/trewartha/positional/compass/ui/CompassNavKey.kt	0.00%	2 Missing ⚠️
...trewartha/positional/location/ui/LocationNavKey.kt	0.00%	2 Missing ⚠️
...trewartha/positional/settings/ui/SettingsNavKey.kt	0.00%	2 Missing ⚠️
...kotlin/io/trewartha/positional/sun/ui/SunNavKey.kt	0.00%	2 Missing ⚠️
...rewartha/positional/core/ui/components/HelpView.kt	0.00%	1 Missing ⚠️
... and 3 more

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