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-003.md

@@ -1,7 +1,7 @@
 ---
 active: true
 derived: false
-header: 'Sensor-Cluster'
+header: 'Sensor cluster'
 level: 1.3
 normative: true
 reviewed: null
@@ -12,27 +12,27 @@ links:
 asil: B
 ---
 
-# SA-003: Sensor-Cluster
+# SA-003: Sensor cluster
 
-## Verantwortung
+## Responsibility
 
-Zusammenfassung aller fuer die EPB benoetigten Eingangssignale:
-Wheel-Speed-Sensoren (4x), Inclinometer (1x), EPB-Schalter, Bremspedal-
-Status, Gear-Position, Door-Open, Seat-Belt — die letzten vier per CAN.
+Summary of all input signals required by the EPB: wheel-speed
+sensors (4x), inclinometer (1x), EPB switch, brake-pedal status,
+gear position, door open, seatbelt — the last four via CAN.
 
-## Schnittstellen
+## Interfaces
 
-| Sensor          | Typ              | Quelle       |
-|-----------------|------------------|--------------|
-| Wheel Speed x4  | Hall-Pulse       | direkt       |
-| Inclinometer    | SPI 1 kHz        | direkt       |
-| EPB-Schalter    | GPIO             | direkt       |
-| Bremspedal      | CAN 0x100        | aus BCM      |
-| Gear            | CAN 0x110        | aus TCU      |
-| Door / Belt     | CAN 0x120        | aus BCM      |
+| Sensor          | Type         | Source     |
+|-----------------|--------------|------------|
+| Wheel speed x4  | Hall pulses  | direct     |
+| Inclinometer    | SPI 1 kHz    | direct     |
+| EPB switch      | GPIO         | direct     |
+| Brake pedal     | CAN 0x100    | from BCM   |
+| Gear            | CAN 0x110    | from TCU   |
+| Door / belt     | CAN 0x120    | from BCM   |
 
-## Nichtfunktionale Eigenschaften
+## Non-functional properties
 
-- Wheel-Speed-Genauigkeit: +/- 0.1 km/h ab 1 km/h
-- Inclinometer-Genauigkeit: +/- 0.5°
-- Sampling-Frequenz Inclinometer: 100 Hz
+- Wheel-speed accuracy: +/- 0.1 km/h above 1 km/h
+- Inclinometer accuracy: +/- 0.5°
+- Inclinometer sampling rate: 100 Hz