[PierreRaybaut]

Closes #536

Summary

French translations replaced the entire card title, including its icon. sphinx-design 0.7 extracts generated SVG in gettext keys, whereas 0.8 excludes icons and can reuse unrelated plain-text translations. Shared reST substitutions now give both versions identical, icon-specific keys. Translated cards retain the same icons as English cards without changes to the Sphinx engine or dependency requirements.

Changes

• Migrate all 41 icon-bearing titles in six pages to |card-icon-NAME| substitutions, defined in doc/_card_icons.txt and included by those pages.
• Migrate their gettext keys and preserve substitution delimiters in 35 translated titles; keep intentionally untranslated entries empty. The substitution-specific keys do not collide with plain-text translations elsewhere.
• Correct the translation convention: preserve substitution delimiters, never copy generated SVG into msgstr.
• Add doc/check_card_icons.py and run it after both HTML builds in documentation CI. It compares title counts and complete SVG markup, and fails explicitly on missing or changed icons.
• Add a user-facing entry to the 1.4.1 documentation release notes with its French translation.

Validation

• Regression demonstrated against the pre-fix French build: contributing/index.html: card title 1 has missing or changed icons (English: 1, French: 0); exit code 1.
• Corrected builds: 41 identical icons in 50 card titles across eight pages, including icon-free titles.
• Fresh gettext extraction and English/French HTML builds pass with -E -W under both sphinx-design 0.7.0 and an isolated 0.8.0 installation. Translation compilation passes.
• All 41 gettext keys are identical across 0.7 and 0.8 and match the catalogs; all French card-title text is translated as intended or intentionally unchanged in both builds.
• SVG markup is identical between English/French builds and between 0.7/0.8 English builds. Non-card icons were checked during prototyping.
• The French release note is present in the rendered HTML.
• Ruff formatting and linting pass for the new script; CI-selection tests: 15 passed.
• Browser validation during prototyping: all eight French home-page icons are visible, with nonzero dimensions and themed fill.
• The user waived a renewed manual-validation stop. No additional manual light/dark theme matrix was performed.
• The first CI run passed all four Python/Qt test jobs; the new icon check exposed the 0.8 incompatibility. After the user's approval, the substitution-based adaptation was implemented and validated with both versions.

Out of scope

None. No application behavior, dependency requirements or release publication changes.

Assisted-by: GPT-6.1 Sol