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

arch/sys/SA-004.md

@@ -1,7 +1,7 @@
 ---
 active: true
 derived: false
-header: 'HMI (Schalter, LED, Display)'
+header: 'HMI (switch, LED, display)'
 level: 1.4
 normative: true
 reviewed: null
@@ -11,17 +11,17 @@ links:
 asil: QM
 ---
 
-# SA-004: HMI (Schalter, LED, Display)
+# SA-004: HMI (switch, LED, display)
 
-## Verantwortung
+## Responsibility
 
-Fahrer-Interaktion und -Information: Tippschalter mit integrierter LED,
-Statusanzeige im Kombi-Display via CAN.
+Driver interaction and information: tap switch with integrated LED,
+status display in the instrument cluster via CAN.
 
-## Schnittstellen
+## Interfaces
 
-| Element       | Typ      | Verhalten                                 |
-|---------------|----------|--------------------------------------------|
-| Tippschalter  | GPIO     | Apply-Richtung / Release-Richtung          |
-| LED           | GPIO     | aus / an / blink 2 Hz / blink 4 Hz         |
-| Display       | CAN 0x3A0 | 50 Hz Status-Frame                        |
+| Element       | Type     | Behaviour                                 |
+|---------------|----------|-------------------------------------------|
+| Tap switch    | GPIO     | apply direction / release direction       |
+| LED           | GPIO     | off / on / blink 2 Hz / blink 4 Hz        |
+| Display       | CAN 0x3A0| 50 Hz status frame                        |