feat(i18n): tools + landing page + doorstop generator in English

Phase 1 of full English translation:
- generate_doorstop_items.py: all 55 items (SG/SYS/SWE/SA/SWA) rewritten in English
- generate_landing_page.py: full UI labels, KPI cards, section headings in English
- traceability.py: docstring, error messages, HTML headers in English
- generate_test_report.py: report content + table headers in English
- All 55 markdown items in safety/sg/, reqs/, arch/ regenerated in English

Still to come:
- demo-epb filled Word docs (PID, plans, safety, manuals, audit artefacts)
- Code comments + test names + CI workflow step names
- README + dev-process repo templates

safety/sg/SG-004.md

@@ -1,7 +1,7 @@
 ---
 active: true
 derived: false
-header: 'Zuverlaessige Hill-Hold-Uebergabe'
+header: 'Reliable hill-hold handover'
 level: 1.4
 normative: true
 reviewed: null
@@ -9,9 +9,9 @@ links: []
 asil: C
 ---
 
-# SG-004: Zuverlaessige Hill-Hold-Uebergabe
+# SG-004: Reliable hill-hold handover
 
-Beim Loslassen des Bremspedals an einem Hang muss die EPB die Bremskraft uebernehmen, bevor das Fahrzeug zu rollen beginnt. Abgeleitet aus HARA-Hazard H-06.
+When the driver releases the brake pedal on an incline, the EPB shall take over the braking force before the vehicle starts rolling. Derived from HARA hazard H-06.
 
 **FTTI:** 500 ms.
-**Safe State:** Apply einleiten.
+**Safe state:** Initiate apply.