fix(web): add missing 'scheduled' key to Kanban i18n types and translations

[junxuku-byte]

The Kanban board added a 'scheduled' column but the TypeScript type
definition in types.ts didn't include it, causing the web UI build
to fail. All 15 translation files (excluding en.ts) were also
missing the 'scheduled' key in both columnLabels and columnHelp.

Changes

• Add scheduled: string to columnLabels and columnHelp in types.ts
• Add 'scheduled' label + help text to all 15 translation files
  (af, de, es, fr, ga, hu, it, ja, ko, pt, ru, tr, uk, zh, zh-hant)

Verification

• npm run build passes successfully
• All translations have both the column label and the descriptive help text

[alt-glitch]

Duplicate of #28534, which adds the same scheduled key translations to all 15 locale files + types.ts. Note that #28549 (merged) already fixed types.ts — the remaining work is the locale translations, which both this PR and #28534 cover identically.

Also note: all non-English translations here are untranslated English strings — maintainers may want actual translations.

[teknium1]

This looks fully implemented on current main by the merged duplicate work in #28534.

Evidence from an automated hermes-sweeper review:

• web/src/i18n/types.ts:778 and web/src/i18n/types.ts:788 already require scheduled: string in columnLabels and columnHelp on current origin/main.
• web/src/i18n/de.ts:711 / web/src/i18n/de.ts:721 and web/src/i18n/zh.ts:707 / web/src/i18n/zh.ts:717 show the locale entries are present with translated strings, rather than the English placeholders from this PR.
• git grep -n "scheduled:" origin/main -- web/src/i18n/... finds the expected 34 entries across types.ts, en.ts, and the 15 non-English locale files.
• The implementing merge is 709e37e19e954774caa3af40a93764bd8b893d35 (fix(dashboard): add scheduled kanban i18n strings (#28534)), which touched the same 16 i18n files.

Thanks for catching the missing key; the fix has landed through the duplicate PR.