Overhaul infrastructure: replace GPU model with rack-centric system

Replace flat GPU buying with a realistic data center + rack pipeline:
- 4 DC tiers (small/medium/large/mega) with construction time, dual
  capacity constraints (rack slots + power budget kW), and era/research
  gating
- 10 predefined rack SKUs from consumer GPUs through custom ASICs, each
  with unique FLOPS, power draw, cost, and pipeline timings
- 6-stage procurement pipeline (order → mfg → receive → install → test
  → production) with Kanban UI, talent-influenced speed bonuses
- Test failures (5-25% base rate) reduced by cooling, ops talent, and QA
  research; auto-repair with cost and re-test cycle
- Production failures at low per-tick rate, racks sent to repair pipeline
- Cooling and redundancy upgrades per DC (reduce failure rates)
- 4 new tech tree nodes (DC Engineering II/III/IV, Quality Assurance)
- Save version bump (1→2) with migration that resets old saves
- Updated economy system to account for rack repair costs
- Redesigned Infrastructure page with pipeline Kanban, capacity bars,
  rack ordering, and DC upgrade panels

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/game-engine/src/data/achievements.ts

@@ -79,11 +79,11 @@ export const ACHIEVEMENT_DEFINITIONS: AchievementDefinition[] = [
     condition: { field: 'meta._eraIndex', operator: 'gte', value: 3 },
   },
   {
-    id: 'gpu-hoarder',
-    name: 'GPU Hoarder',
-    description: 'Own 100 or more GPUs across all data centers.',
+    id: 'rack-hoarder',
+    name: 'Rack Hoarder',
+    description: 'Have 50 or more production racks across all data centers.',
     icon: 'Cpu',
-    condition: { field: 'infrastructure._totalGpuCount', operator: 'gte', value: 100 },
+    condition: { field: 'infrastructure.totalRackCount', operator: 'gte', value: 50 },
   },
   {
     id: 'research-pioneer',