feat(i18n): overhaul translations and keep language dropdown inside a…

[Natixe]

Overhaul the Arabic, French, and Spanish localization catalogs and fix the
language dropdown positioning so it always remains accessible inside the app
window.

The language dropdown was fixed-positioned without coordinates, so it fell back
to its static position and grew downwards from the middle of the dialog. With 9
locales at 56px each (~536px of list), it ran past the bottom of the window and
the last languages were unreachable. Its max-height: calc(100vh - 400px) used
a hardcoded offset that did not match where the trigger actually sits, causing
overflow on tall windows and truncating the list too early on short ones.

Language dropdown changes:

• compute the dropdown placement dynamicall
  y from the trigger's bounding rect
• set top, left, width, and max-height based on the available space up to the
  window edge
• keep the locale list scrollable inside the dropdown instead of overflowing
  outside the page
• flip the dropdown upwards when there is not enough room below and more space
  is available above
• reposition the dropdown on window resize
• reposition it on scroll using the capture phase, since the dialog content can
  scroll and a fixed dropdown would otherwise detach from its trigger
• close the dropdown when the dialog closes to avoid reopening it at a stale
  position
• remove the hardcoded width, max-height, and margin rules from the stylesheet

Internationalization changes:

• improve and harmonize UI and Wallet translations in Arabic, French, and Spanish
• add missing translation keys and remove incorrect keys
• fix placeholders, HTML tags, and CLDR plural forms
• standardize technical terminology related to CKB and Neuron
• remove remaining English strings and typographical errors
• add an i18n audit script to automatically validate translation catalogs

(Basically, adding to and improving the work I had already done )