Working prototype with dev dashboard

- Created core Engine that coordinates all subsystems
- Extended API with comprehensive endpoints for dev dashboard
- Implemented pure Go vision processing (no GoCV dependency)
- Built full-featured dev dashboard with live capture viewer, region overlays, pixel inspector
- Added D2R detector with actual health/mana reading from orb regions
- Fixed resolution profile registration and region validation
- Generated synthetic test data for development
- Added dev mode support with file backend for testing
- Fixed build tag issues for cross-platform compilation

Prototype features:
✅ Live capture viewer with region overlays
✅ Real-time state detection (game state, health %, mana %)
✅ Pixel inspector (hover for RGB/HSV values)
✅ Capture stats monitoring (FPS, frame count)
✅ Region management with toggle visibility
✅ File upload for testing screenshots
✅ Dark theme dev-focused UI
✅ CORS enabled for dev convenience

Ready for: go run ./cmd/iso-bot --dev --api :8080

pkg/engine/capture/capture.go

@@ -97,3 +97,13 @@ func (m *Manager) Stats() Stats {
 func (m *Manager) Close() error {
 	return m.source.Close()
 }
+
+// Source returns the underlying capture source.
+func (m *Manager) Source() Source {
+	return m.source
+}
+
+// Size returns the source dimensions.
+func (m *Manager) Size() (width, height int) {
+	return m.source.Size()
+}