chore: review French user-facing strings

[zefutoff]

Summary

• review user-facing French wording across the application
• normalize French typography and apostrophes
• replace ASCII ellipses with typographic ellipses
• remove artificial plurals such as problème(s)
• use Android plural resources for dynamic counts
• fix diagnostic wording and spelling
• harmonize correction-mode terminology across screens
• rename the 1990 dictionary option to Rectifications de 1990
• reuse string resources for manifest labels
• remove obsolete unused string resources
• complete the Phase 4 French-string review roadmap item

Validation

• targeted French-string audit reports no remaining issues
• no artificial dynamic plurals remain in app/src/main
• make check
• make assemble
• git diff --check
• final APK does not request android.permission.INTERNET

Roadmap

Completes:

• Review all user-facing French strings