ADFA-5309 chore(strings): dead-string cleanup + one-pass re-localization

[luisguzman-adfa]

Part of the K2Go string cleanup/unification (ADFA-5309). Two things, landed in
waves to keep each step reviewable:

1. Dead-string cleanup. Removed 81 strings that nothing references — found by a
   two-pass check (no R.string. in any .java, no @string/ in any
   layout/menu/xml/drawable/values file; no getIdentifier() in the module, so the
   list is authoritative). These are old-UI leftovers, variants superseded by the
   live UI (e.g. maps_choose_cta -> live maps_choose_title, zim_lang_sub -> live
   zim_lang_state_system), and stale "coming soon" placeholders. Removed from the
   default and all 33 locales; catalog 817 -> 736.

2. One-pass re-localization. The English copy updated in ADFA-5304 was English-only
   at merge; this PR brings the 33 locales back in sync for the ~121 changed
   strings, committed in waves by area (clone/connect, modules + get more, maps +
   backup/restore, setup/wizard/permissions, auth/settings + misc). Locale strings
   are machine-translated, flagged for native review (bn/gu/ta/sw/az/yo/sr).

Strings only — no code or layout changes. XML validated across default + 33 locales
after each wave.

Deferred (not in this PR):

• Merging strings_k2go.xml into a single strings.xml — held until branch churn
  settles, to avoid mass conflicts with in-flight feature branches.
• Removing the unreachable share_anyway trio, which needs the CloneFragment
  dead-branch removal — separate review.