fix(#1240): fix overall balance to stay anchored to today across calendar navigation

[rbalogic]

Summary

Fixes #1240.

Overall Balance now stays anchored to the real current day, even when navigating to past or future dates in Month/Day views.

What Changed?

• Anchored Overall Balance calculations to today in both Month and Day views
• Preserved existing count-today behavior
• Updated English tooltip copy to match implemented behavior
• Added renderer test coverage for past/future navigation in both calendar views
• Stabilized the calendar window wait-mode renderer test

Why This Change?

Navigating the calendar previously made Overall Balance appear to shift with the viewed date.
This update keeps the metric fixed to today for consistent, predictable behavior.

Testing

npm run test:electron-mocha

npx eslint \
  renderer/classes/BaseCalendar.js \
  renderer/classes/MonthCalendar.js \
  renderer/classes/DayCalendar.js \
  __tests__/__renderer__/calendar.mjs \
  __tests__/__renderer__/classes/MonthCalendar.mjs \
  __tests__/__renderer__/classes/DayCalendar.mjs \
  --config configs/eslint.config.mjs

npx prettier -c locales/en/translation.json --config configs/.prettierrc.json

Notes

• No screenshots included: behavior change only, plus a tooltip text update.

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[rbalogic]

@tupaschoal Please review this PR when you can and approve workflow if required, Thanks.