feat(economy): Sprint 2.1 — wire Tier-2/Tier-3 production chains end-to-end

[Copilot]

Tier-2 and Tier-3 production was computing at flat rates without enforcing input dependencies — T3 buildings produced freely regardless of T2 stock. The production flow had no UI representation.

Backend (api/economy_flush.php)

• Added ECONOMY_TIER3_INPUT_RATIOS constant mapping each T3 good to its required T2 inputs + consumption ratios (mirrors EconomySimulation.js recipes)
• T3 buildings now drive T2 consumption rates; T3 output rate is scaled down proportionally when T2 stock is insufficient:

// e.g. consumer_goods requires steel_alloy × 1.0 + electronics_components × 1.0
'consumer_goods' => [['steel_alloy', 1.0], ['electronics_components', 1.0]],

API (api/economy.php — get_production)

• Added chain_status to the response: per T3 good, reports ok/low/starved, per-input stock levels (qty, capacity, pct), and output stock — all derived from current T2 stock after flush.

Frontend (js/engine/runtime/RuntimeEconomyController.js)

• Bug fix: warningHtml in _renderOverviewTab was declared after an early return — war/pirate conflict banners were never rendered in the overview tab.
• Added ⛓ Production tab with a per-colony Tier-2 → Tier-3 chain visualizer:
  • Each chain node is color-coded 🟢 ≥50% / 🟡 10–50% / 🔴 <10% capacity
  • T3 nodes surface their T2 input stocks inline
  • Per-colony bottleneck warnings from economyBottleneck
  • Conflict banner (war / pirate damage) carried through to this tab

Tests (tests/js/runtime-economy-controller.test.js)

• 18 new unit tests covering: three-tab HTML structure, T2 all-building production, T3 blocked when T2 inputs absent, multi-tick depletion, PROCESSING_RECIPES Tier-3 input validity