Tranche 1: mobile polish, calendar, and stats refresh

[feragusper]

Summary

• complete tranche 1 of the backlog delivery plan
• strengthen mobile History calendar mode
• clean up post-0.7 settings and home guidance
• refresh mobile stats presentation to match the stronger web direction

Included issues

• closes Add calendar view to mobile History #143
• closes Refresh mobile charts with a stronger visual system #147
• closes Polish post-0.7 Settings and Home guidance UX #149

What changed

• mobile History calendar now supports month navigation and monthly context
• Settings no longer shows the lingering saved footer and now explains points in a dedicated card
• Home removes the confusing streak callout and keeps only the clearer points signal
• mobile Stats now uses summary cards, calmer chart framing, and a more intentional visual hierarchy

Verification

• ./gradlew :features:settings:presentation:mobile:testDebugUnitTest
• ./gradlew :features:history:presentation:mobile:compileDebugKotlin
• ./gradlew :features:stats:presentation:mobile:testDebugUnitTest
• ./gradlew :apps:mobile:assembleStagingDebug
• ./gradlew :apps:web:jsBrowserDevelopmentWebpack
• ./gradlew check