feat(camera): implement 2x zoom out

[Copilot]

Adds 2x zoom out (0.5 scale factor) to increase visible game area from 1280×720 to 2560×1440 effective pixels.

Implementation

• Added zoomLevel property to RenderSystem (default: 0.5)
• Camera now calculates visible bounds as canvas.dimensions / zoomLevel
• Applied ctx.scale() transformation before camera translation (order matters for correct offset calculation)
• UI elements (HUD, stats, health bar) rendered outside scaled context

// Camera calculates larger visible area
const visibleWidth = this.canvas.width / this.zoomLevel;   // 2560px
const visibleHeight = this.canvas.height / this.zoomLevel; // 1440px

// Transformations applied in sequence
ctx.scale(this.zoomLevel, this.zoomLevel);  // Zoom first
ctx.translate(-this.cameraX, -this.cameraY); // Then translate

Result

Players see 4x more surface area (2× width, 2× height) while UI remains unscaled.

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