feat: add application visual identity

[zefutoff]

Summary

• add a dedicated visual identity for Grammalecte Android
• add an adaptive launcher icon
• add Android 13+ monochrome themed icon support
• add a matching Quick Settings icon
• add branded accent colors for light and dark themes
• use the brand accent on the main application title
• keep the full application label for system surfaces
• use a concise Grammalecte launcher label
• add instrumentation coverage for icon and label wiring
• complete the Phase 4 visual identity roadmap item

Visual identity

The icon uses:

• an indigo background
• a document symbol
• a green correction check mark

The design is original to this Android integration and does not reuse the official Grammalecte logo.

Validation

• launcher icon manually validated on Samsung Galaxy S21
• recent-apps icon manually validated
• Quick Settings icon manually validated
• dark-theme visual identity manually validated
• concise launcher label manually validated
• VisualIdentityManifestTest passes
• make check
• make assemble
• git diff --check
• final APK does not request android.permission.INTERNET

Roadmap

Completes:

• Application icon and visual identity