Update Russian translation and README_rus.md

[NilaierMusic]

Description:
This pull request updates and improves the Russian translation for the application. Specifically, it addresses missing strings by adding translations for 235 strings and removing out-of-date entries that are no longer in the original source text. In addition, README_rus.md is updated to match the latest content in the main README.md.

Summary of Changes:

1. ru.axaml – Added or updated translations for all relevant strings.
2. Removed out-of-date strings – Cleaned up translation entries that no longer exist in the original.
3. README_rus.md – Brought in line with the main README.md for consistency.

Known Issues / Additional Notes:

• The resource string <sys:String x:Key="not_available">Недоступно</sys:String> does not seem to appear in certain contexts (e.g., Usage Report and Metering Report), which still display “Not available” instead of “Недоступно.” This might indicate hard-coded or differently referenced strings outside the resource file.
• There are additional hard-coded strings in BluetoothService.cs (e.g., error messages and logs) as well as a button label in MainView.axaml that are not currently pulling from the translation resources. These lines will require further refactoring to make them translatable in the future.

Testing & Verification:

• Verified new translations appear correctly where resource-based strings are used.
• Confirmed there are no untranslated or orphaned strings in ru.axaml.
• Checked README_rus.md for full alignment with the main README.md.

Next Steps:

• Address any remaining hard-coded strings by refactoring them into resource files to ensure full localization coverage.
• Confirm the “Not available” usages for reports are correctly bound to the not_available resource string.

Please let me know if there are any further concerns or if you spot additional untranslated items!