i18n(tr): add Turkish UI translation catalog (#3809)

Add Turkish (tr) translation catalog covering 100% of measured UI strings (1,727/1,727 keys, 3,731 catalog entries).

- Register Turkish language in crates/ui-egui/src/i18n/mod.rs with complete_menus: true and plural_none
- Add tr.tsv translation catalog
- Add negotiation and coverage tests in system.rs, mod.rs and i18n_coverage.rs
- Add MIT OR Apache-2.0 notice in LICENSE-translations.txt
- Update docs/localization-parity.md

Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

xtask/src/i18n_coverage.rs

@@ -579,6 +579,7 @@ mod tests {
             ("el", "el.tsv"),
             ("uk", "uk.tsv"),
             ("nl", "nl.tsv"),
+            ("tr", "tr.tsv"),
             ("vi", "vi.tsv"),
         ] {
             let catalog_path = root.join("crates/ui-egui/src/i18n").join(path);