chore(i18n): complete missing translations and fix translation bugs across all 26 locales

[ethicnology]

Full pass over localization/ to bring every non-English locale to 100% key
parity with the en template, and to fix a batch of pre-existing translation
bugs found along the way. app_en.arb is untouched.

Tooling (tools/arb.dart)

Extended the existing ARB tool with commands needed to do this at scale
without hand-editing 26 large files:

• missing-detail LOCALE — export a locale's missing keys as
  {key: {en, description, placeholders}} JSON, ready to translate.
• fill LOCALE --translations-file — bulk-add/update many translations in
  one pass instead of one set call per key.
• audit-identical — flag values byte-identical to the en template (a
  likely untranslated copy-paste).
• audit-placeholders — flag values whose top-level {placeholder} tokens
  don't match the en template's. Walks ICU brace depth so the literal case
  bodies of a {var, plural, =1{...} other{...}} block aren't misread as
  extra placeholders (a naive regex previously false-positived on every
  locale for one key).

Translations (localization/*.arb)

• Filled every missing key across all 26 locales (ar, as, bg, bn, cs, de,
  el, es, fa, fi, fr, hi, hi_Latn, hy, it, ka, ko, pt, pt_BR, ru, sw, th, tr,
  uk, vi, zh). hy, ka, sw, vi were previously only ~8–10% translated;
  every other locale had between 106 and 864 keys missing out of 3416.
• Fixed ~65 pre-existing placeholder bugs across 16 locales — a
  {placeholder} (e.g. {error}, {device}, {amount}) silently dropped
  in a past translation, in several cases replaced by garbled artifacts
  (e.g. "X64X", "页: 1") from some earlier broken translation tool.
• Translated ~400 strings that existed as untranslated, byte-identical
  copies of the en text despite the key already being present in the file.

Out of scope (follow-ups, not done here)

• A few existing (non-missing) translations were flagged by reviewing
  agents as simply wrong (not missing/identical, just incorrect), e.g. in
  Thai: "Failed" translated as a word meaning "house", "sats" as "sit down".
  These weren't touched here — worth a dedicated native-speaker review pass.
• liquidRiskDisclosureBody untouched

[claude]

Claude finished @ethicnology's task in 14m 57s —— View job

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PR Review in progress

• Gather context (diff vs origin/develop)
• Review tools/arb.dart new commands for correctness bugs
• Validate all 26 ARB files (key parity ✓, placeholder counts ✓, ICU brace balance ✓, script-correctness of rebuilt locales ✓)
• Scan for encoding artifacts / wrong-script contamination
• Sample translation quality across locales (5 parallel reviewers running)
• Check CI (gen-l10n / analyze) result
• Post findings + summary