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-005.md

@@ -1,7 +1,7 @@
 ---
 active: true
 derived: false
-header: 'Reaktion auf Fahreranforderung'
+header: 'Response to driver requests'
 level: 1.5
 normative: true
 reviewed: null
@@ -9,8 +9,8 @@ links: []
 asil: B
 ---
 
-# SG-005: Reaktion auf Fahreranforderung
+# SG-005: Response to driver requests
 
-Das System muss in spezifizierter Zeit auf Fahrer-Apply- und Release-Anforderungen reagieren. Abgeleitet aus HARA-Hazards H-03 und H-07.
+The system shall respond to driver apply and release requests within specified times. Derived from HARA hazards H-03 and H-07.
 
-**Reaktionszeit:** Apply <= 800 ms, Release <= 1500 ms.
+**Response time:** apply <= 800 ms, release <= 1500 ms.