refactor(effects): Factor shared initialization into Effect base class

Eliminate ~100 lines of duplicated code across effect subclasses by moving common resource initialization to the base Effect class. Most effects repeatedly created uniforms buffers, samplers, and dummy textures with identical configurations.

Changes:
- Add shared members to Effect: uniforms_buffer_, sampler_, dummy_texture_*
- Add helpers: init_uniforms_buffer(), create_*_sampler(), create_dummy_scene_texture()
- Add gpu_create_*_sampler() and gpu_create_dummy_scene_texture() to gpu.h
- Move HEADLESS_RETURN_IF_NULL to Effect constructor
- Update 7 effects to use base class helpers (Flash, Heptagon, Passthrough, Placeholder, GaussianBlur, Particles, PeakMeter)

Benefits: Improved consistency, easier maintenance, reduced binary size.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 0 insertions, 2 deletions

diff --git a/src/effects/gaussian_blur_effect.h b/src/effects/gaussian_blur_effect.h
index cc9ff56..f4b8fcf 100644
--- a/src/effects/gaussian_blur_effect.h
+++ b/src/effects/gaussian_blur_effect.h
@@ -26,8 +26,6 @@ class GaussianBlur : public Effect {
  private:
   WGPURenderPipeline pipeline_;
   WGPUBindGroup bind_group_;
-  WGPUSampler sampler_;
   GaussianBlurParams blur_params_;
   UniformBuffer<GaussianBlurParams> params_buffer_;
-  UniformBuffer<UniformsSequenceParams> uniforms_buffer_;
 };