Heatsinks, wider 12 V tracks, design review; pause project

- PCB rev 0.1: Power3A class (1.5 mm) for the 12 V input path, Aavid
  clip-on heatsinks on Q3/Q5/Q6 (project footprint library), T-junction
  healing and via shrink in the router; DRC 0 errors
- Current-capacity and heatsink documentation
- CLAUDE.md with project decisions, workflow and gotchas
- docs/design-review.md: review of a module-only PSU (rev 0.2) and cost
  estimate
- Project paused for budget and safety reasons

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/bom.md

@@ -33,7 +33,7 @@ Prices are rough estimates.
 | 2 | 330 kΩ ½ W | R6, R11 | R6, R7 |
 | 1 | 2 kΩ 5 W | R13 | R8 |
 | 3 | 0.1 µF 500 V film | C6, C8, C9 | C3, C4, C7 |
-| 3 | TO-220 heatsink | for Q3, Q5, Q6 | |
+| 3 | Aavid 576802B03900G clip-on heatsink (~20 K/W), **live**: one per transistor, must not touch | HS1–HS3 on Q3, Q5, Q6 | |
 
 ## Additions