Add post-processing audio effects system

Adds a full effects pipeline powered by Spotify's pedalboard library,
enabling users to apply professional DSP effects (flanger, reverb, delay,
compressor, pitch shift, filters, gain) to generated audio.

Key features:
- Effects chain editor with drag-and-drop reordering (dnd-kit)
- Generation versions: clean copy always saved, processed versions created on top
- Built-in presets (Robotic, Radio, Echo Chamber, Deep Voice) + custom user presets
- Per-profile default effects chain (auto-applied to new generations)
- Per-generation effects override from the generation form
- Apply effects to existing generations from history (creates new version)
- Ephemeral preview endpoint for auditioning effects without persisting
- Dedicated Effects sidebar tab with preset management and live preview
- Version switcher in history cards with expandable panel
- Backward-compatible: existing generations backfilled as clean versions

app/src/lib/api/client.ts

@@ -2,9 +2,15 @@ import type { LanguageCode } from '@/lib/constants/languages';
 import { useServerStore } from '@/stores/serverStore';
 import type {
   ActiveTasksResponse,
+  ApplyEffectsRequest,
+  AvailableEffectsResponse,
   CudaStatus,
+  EffectConfig,
+  EffectPresetCreate,
+  EffectPresetResponse,
   GenerationRequest,
   GenerationResponse,
+  GenerationVersionResponse,
   HealthResponse,
   HistoryListResponse,
   HistoryQuery,
@@ -583,6 +589,93 @@ class ApiClient {
 
     return response.blob();
   }
+
+  // Effects & Versions
+  async getAvailableEffects(): Promise<AvailableEffectsResponse> {
+    return this.request<AvailableEffectsResponse>('/effects/available');
+  }
+
+  async listEffectPresets(): Promise<EffectPresetResponse[]> {
+    return this.request<EffectPresetResponse[]>('/effects/presets');
+  }
+
+  async createEffectPreset(data: EffectPresetCreate): Promise<EffectPresetResponse> {
+    return this.request<EffectPresetResponse>('/effects/presets', {
+      method: 'POST',
+      body: JSON.stringify(data),
+    });
+  }
+
+  async deleteEffectPreset(presetId: string): Promise<void> {
+    await this.request<void>(`/effects/presets/${presetId}`, {
+      method: 'DELETE',
+    });
+  }
+
+  async listGenerationVersions(generationId: string): Promise<GenerationVersionResponse[]> {
+    return this.request<GenerationVersionResponse[]>(`/generations/${generationId}/versions`);
+  }
+
+  async applyEffectsToGeneration(
+    generationId: string,
+    data: ApplyEffectsRequest,
+  ): Promise<GenerationVersionResponse> {
+    return this.request<GenerationVersionResponse>(
+      `/generations/${generationId}/versions/apply-effects`,
+      {
+        method: 'POST',
+        body: JSON.stringify(data),
+      },
+    );
+  }
+
+  async setDefaultVersion(
+    generationId: string,
+    versionId: string,
+  ): Promise<GenerationVersionResponse> {
+    return this.request<GenerationVersionResponse>(
+      `/generations/${generationId}/versions/${versionId}/set-default`,
+      { method: 'PUT' },
+    );
+  }
+
+  async deleteGenerationVersion(generationId: string, versionId: string): Promise<void> {
+    await this.request<void>(`/generations/${generationId}/versions/${versionId}`, {
+      method: 'DELETE',
+    });
+  }
+
+  getVersionAudioUrl(versionId: string): string {
+    return `${this.getBaseUrl()}/audio/version/${versionId}`;
+  }
+
+  async updateProfileEffects(
+    profileId: string,
+    effectsChain: EffectConfig[] | null,
+  ): Promise<VoiceProfileResponse> {
+    return this.request<VoiceProfileResponse>(`/profiles/${profileId}/effects`, {
+      method: 'PUT',
+      body: JSON.stringify({ effects_chain: effectsChain }),
+    });
+  }
+
+  async previewEffects(generationId: string, effectsChain: EffectConfig[]): Promise<Blob> {
+    const url = `${this.getBaseUrl()}/effects/preview/${generationId}`;
+    const response = await fetch(url, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ effects_chain: effectsChain }),
+    });
+
+    if (!response.ok) {
+      const error = await response.json().catch(() => ({
+        detail: response.statusText,
+      }));
+      throw new Error(error.detail || `HTTP error! status: ${response.status}`);
+    }
+
+    return response.blob();
+  }
 }
 
 export const apiClient = new ApiClient();