feat(ihk): add complete AP2 courses for ITSE, ITSM, and KDM (ZPA 2. Auflage)
- Added 36 brand-new AP2 chapters with 4 tracks each:
* ihk_ap2_itse (IT-System-Elektroniker/in): DIN VDE 0100/0701, DGUV V3, USV (VFI), LWL/OTDR, EMV, 40h-Projekt
* ihk_ap2_itsm (Kaufleute für IT-System-Management): 7P-Marketing, Handelskalkulation, TCO/ROI, EVB-IT, SLAs, 40h-Projekt
* ihk_ap2_kdm (Kaufleute für Digitalisierungsmanagement): Business Model Canvas, Plattformökonomie, BPMN 2.0, GoBD-DMS, XRechnung, DSFA/AI Act, 40h-Projekt
- Created interactive tools:
* usv_calculator.js (Wirk-, Scheinleistung, Autonomiezeit & Redundanz N+1)
* handelskalkulation_trainer.js (LEP -> Rabatt -> ZVP -> BVP Vorwärtskalkulation)
- Expanded official IHK question bank to 219 questions (+12 authentic ITSE/ITSM/KDM items)
- Integrated into courses_manifest.js, it_ausbildungen_manifest.js, and dashboard.html
- Resolved all relative paths (zero 404 errors verified across 2,428 links)
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