fix(report-ui): fix language and onHover Tooltip alignment

[huzky-v]

Summary

Translate the /reports dashboard page from Portuguese to English user-facing labels, extract a shared ChartTooltip component to unify chart tooltip styling, and revert the CI placeholder-check approach in favor of job-level if gating.

Type of change

• fix: — bug fix (no behavior change beyond the bug)
• feat: — new user-facing feature or capability
• refactor: — internal refactor (no behavior change, no API change)
• docs: — documentation only
• chore: / ci: / build: — tooling, CI, packaging
• test: — test-only change
• Breaking change

Linked issue:

OpenSpec

• This PR includes / updates an OpenSpec change
• Not applicable — bug fix that matches the existing spec
• Not applicable — docs / CI / chore only
• This PR touches a codex-faithful path (image pipeline, request/response
  shape, SSE framing, OAuth flow) and preserves upstream-equivalent behavior

Change directory: openspec/changes/translate-reports-ui-english/

Changes

• Reports page: translate all page-owned Portuguese labels to English (Cost Report, Usage history by date range, Loading..., Total Cost, Cost by Day, Tokens by Day, Distribution by Model, Daily Breakdown, etc.)
• Extract shared ChartTooltip component (chart-tooltip.tsx) with Partial<TooltipContentProps> typing for recharts v3.8.1 compatibility, replacing inline tooltip styling in cost-per-day-chart.tsx, tokens-per-day-chart.tsx, and model-distribution-donut.tsx
• CI: revert the placeholder-step approach for pytest/postgres matrix jobs; use job-level if: needs.changes.outputs.backend == 'true' instead, removing the skip steps and per-step if guards
• Remove obsolete OpenSpec change create-pytest-required-check-placeholders/ and its regression tests
• Add OpenSpec change translate-reports-ui-english/ with proposal, delta spec, and tasks
• Sync frontend-architecture main spec with the new reports-page English wording requirements

Test plan

# Frontend type-check
cd frontend && npx tsc -b

# OpenSpec validation
openspec validate translate-reports-ui-english --strict

# Existing backend tests
uv run pytest tests/ -q

Checklist

• Title is in Conventional Commits format (<type>(<scope>)?: <subject>).
• Linked the related issue / discussion above.
• Added or updated tests covering the change.
• Ran uv run pre-commit run local-ci --hook-stage manual --all-files or the relevant make <target> subset locally.
• If touching specs: openspec validate --specs passes and /opsx:verify is clean.
• CHANGELOG is not edited by hand (release-please handles it).

[huzky-v]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🚀

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