#498: French (fr) interface translation

Problem: French, one of Premiere's interface languages and one of the
12 key languages in docs/gaps.md G14, had no catalog; #498 asked for it.

Fix: a new fr.tsv catalog with every entry Spanish has (menus, panels,
dialogs, Settings pages, the Effects / Effect Controls registry, the
Keyboard Shortcuts dialog, status messages) plus the native macOS
Settings item, written from the plain meaning of the English text with
ordinary French editing vocabulary (infinitive commands, "vous", French
sentence case and spacing). Language::Fr is persisted as `fr`;
app.language.french joins Edit > Language (checkmark, native macOS menu),
Settings > General offers Français, and System Language picks French for
any fr-* locale. Like Japanese, tests require only the core menus, so
later strings show in English until translated; a French entry without
a Spanish one fails. A new test checks the bundled fonts cover every
French letter (the glyph check is shared with Ukrainian). Docs: G14,
localization-parity, ROADMAP language row, ui-egui README.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

ATTRIBUTION.md

@@ -9,6 +9,7 @@ iconography, images or other Adobe assets; open licences only; every asset attri
 
 | Asset | Author | Source | Licence |
 |---|---|---|---|
+| `crates/ui-egui/src/i18n/fr.tsv` | FilmCraft contributors | Original work: clean-room French interface translations | MIT OR Apache-2.0 |
 | `crates/ui-egui/src/i18n/ru.tsv` | FilmCraft contributors | Original work: clean-room Russian interface translations | MIT OR Apache-2.0 |
 | `crates/ui-egui/src/i18n/uk.tsv` | FilmCraft contributors | Original work: clean-room Ukrainian interface translations | MIT OR Apache-2.0 |
 | `assets/fonts/Inter-Regular.ttf` | The Inter Project Authors | https://github.com/rsms/inter | OFL-1.1 (`assets/fonts/OFL-Inter.txt`) |