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/techTree.ts

@@ -25,32 +25,32 @@ export const TECH_TREE: ResearchNode[] = [
   {
     id: 'advanced-gpu-arch',
     name: 'Advanced GPU Architecture',
-    description: 'Unlocks procurement of NVIDIA A100 datacenter GPUs.',
+    description: 'Unlocks procurement of NVIDIA A100 rack configurations.',
     era: 'startup',
     category: 'infrastructure',
     prerequisites: [],
     cost: { researchPoints: 0, compute: 10, ticks: 90 },
-    effects: [{ type: 'unlock_gpu', target: 'a100', value: 1 }],
+    effects: [{ type: 'unlock_rack', target: 'a100', value: 1 }],
   },
   {
     id: 'next-gen-gpu',
     name: 'Next-Gen GPU Architecture',
-    description: 'Unlocks procurement of NVIDIA H100 GPUs.',
+    description: 'Unlocks procurement of NVIDIA H100 rack configurations.',
     era: 'scaleup',
     category: 'infrastructure',
     prerequisites: ['advanced-gpu-arch'],
     cost: { researchPoints: 2, compute: 40, ticks: 240 },
-    effects: [{ type: 'unlock_gpu', target: 'h100', value: 1 }],
+    effects: [{ type: 'unlock_rack', target: 'h100', value: 1 }],
   },
   {
     id: 'frontier-compute',
     name: 'Frontier Compute',
-    description: 'Unlocks procurement of NVIDIA B200 GPUs.',
+    description: 'Unlocks procurement of NVIDIA B200 rack configurations.',
     era: 'bigtech',
     category: 'infrastructure',
     prerequisites: ['next-gen-gpu'],
     cost: { researchPoints: 5, compute: 200, ticks: 480 },
-    effects: [{ type: 'unlock_gpu', target: 'b200', value: 1 }],
+    effects: [{ type: 'unlock_rack', target: 'b200', value: 1 }],
   },
   {
     id: 'custom-silicon',
@@ -60,7 +60,47 @@ export const TECH_TREE: ResearchNode[] = [
     category: 'infrastructure',
     prerequisites: ['frontier-compute'],
     cost: { researchPoints: 10, compute: 500, ticks: 900 },
-    effects: [{ type: 'unlock_gpu', target: 'custom', value: 1 }],
+    effects: [{ type: 'unlock_rack', target: 'custom', value: 1 }],
+  },
+  {
+    id: 'dc-engineering-ii',
+    name: 'DC Engineering II',
+    description: 'Advanced facility design unlocks Medium data centers (30 slots, 200kW).',
+    era: 'startup',
+    category: 'infrastructure',
+    prerequisites: ['advanced-cooling'],
+    cost: { researchPoints: 1, compute: 15, ticks: 120 },
+    effects: [{ type: 'unlock_dc_tier', target: 'medium', value: 1 }],
+  },
+  {
+    id: 'dc-engineering-iii',
+    name: 'DC Engineering III',
+    description: 'Large-scale facility design unlocks Large data centers (60 slots, 500kW).',
+    era: 'scaleup',
+    category: 'infrastructure',
+    prerequisites: ['dc-engineering-ii'],
+    cost: { researchPoints: 3, compute: 60, ticks: 300 },
+    effects: [{ type: 'unlock_dc_tier', target: 'large', value: 1 }],
+  },
+  {
+    id: 'dc-engineering-iv',
+    name: 'DC Engineering IV',
+    description: 'Mega-scale campus design unlocks Mega data centers (120 slots, 1200kW).',
+    era: 'bigtech',
+    category: 'infrastructure',
+    prerequisites: ['dc-engineering-iii'],
+    cost: { researchPoints: 6, compute: 150, ticks: 600 },
+    effects: [{ type: 'unlock_dc_tier', target: 'mega', value: 1 }],
+  },
+  {
+    id: 'quality-assurance',
+    name: 'Quality Assurance',
+    description: 'Advanced QA processes reduce rack test failure rate by 25%.',
+    era: 'startup',
+    category: 'infrastructure',
+    prerequisites: ['redundancy-protocols'],
+    cost: { researchPoints: 1, compute: 10, ticks: 90 },
+    effects: [{ type: 'cost_reduction', target: 'test_failure_rate', value: 0.25 }],
   },
   {
     id: 'distributed-training',