fix(i18n): translate assignee picker strings

[viktormarinho]

Summary

Fixed hardcoded user-facing strings in the assignee picker component that should have been localized.

Invariant Violated

No hardcoded user-facing strings — JSX placeholders, labels, and empty states must go through t().

Evidence (Before)

apps/web/src/layouts/task-board/assignee-picker.tsx:
- Line 24: placeholder="Assign to…"
- Line 26: >No members found.<
- Line 37: value="Unassigned"
- Line 42: >Unassigned<
- Line 45: heading="Members"

Fix Applied

Updated component to use i18n via useT():

• placeholder="Assign to…" → t("taskBoard.taskDialog.assignToPlaceholder")
• >No members found. → t("taskBoard.taskDialog.noMembersFound")
• value="Unassigned" → t("taskBoard.taskDialog.unassignedLabel")
• heading="Members" → t("taskBoard.taskDialog.membersGroupHeading")

All translation keys were already present in both en and pt-br dictionaries with proper translations.

Evidence (After)

Verification with hardcoded string heuristic checks:

$ rg 'placeholder="Assign to…"' apps/web/src/layouts/task-board/assignee-picker.tsx
# No matches (was: present on line 24)

$ rg '>No members found\.' apps/web/src/layouts/task-board/assignee-picker.tsx
# No matches (was: present on line 26)

$ rg 'heading="Members"' apps/web/src/layouts/task-board/assignee-picker.tsx
# No matches (was: present on line 45)

Infrastructure

Set up i18n domain directory (domains/i18n/) with:

• DOMAIN.md — domain invariants and enforcement rules
• quality.md — pt-br translation quality guidelines
• triage.md — hardcoded-string triage ledger (empty; first run)
• quality-baseline — baseline commit SHA for subjective quality audits

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Summary by cubic

Localized the assignee picker by replacing hardcoded text with t(), and added i18n domain guardrails. Also applied Biome formatting.

• Bug Fixes

  • Switched to useT() in assignee-picker.tsx.
  • Placeholder → t("taskBoard.taskDialog.assignToPlaceholder")
  • Empty state → t("taskBoard.taskDialog.noMembersFound")
  • "Unassigned" label/value → t("taskBoard.taskDialog.unassignedLabel")
  • "Members" heading → t("taskBoard.taskDialog.membersGroupHeading")

• Infrastructure

  • Added domains/i18n/ with DOMAIN.md, quality.md, triage.md, and quality-baseline to enforce “no hardcoded strings,” pt-br parity, and quality rules.
  • Applied Biome formatting.

^{Written for commit c233758. Summary will update on new commits.}