Add total investment roll-up: 4M-7.7M EUR full vision, 1.5M-2.5M EUR phased entry

All sums and conversions reviewer-recomputed; every block carries its
basis (quote, researched range, or marked estimate)

README.md

@@ -92,6 +92,9 @@ The detail lives in dedicated documents:
 - [Project scale](docs/scale.md): rough numbers for everything on one page:
   output capacity, building area, land, electrical demand, solar and
   storage, steam and fuel, headcount, and money cross-references
+- [Total investment](docs/finance/total-investment.md): the full-vision
+  roll-up (~4M to 7.7M EUR) and the ~1.5M to 2.5M EUR phased entry, with
+  the basis of every block
 
 ## Repository Layout