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/hooks/useGenerationForm.ts

@@ -4,6 +4,7 @@ import { useForm } from 'react-hook-form';
 import * as z from 'zod';
 import { useToast } from '@/components/ui/use-toast';
 import { apiClient } from '@/lib/api/client';
+import type { EffectConfig } from '@/lib/api/types';
 import { LANGUAGE_CODES, type LanguageCode } from '@/lib/constants/languages';
 import { useGeneration } from '@/lib/hooks/useGeneration';
 import { useModelDownloadToast } from '@/lib/hooks/useModelDownloadToast';
@@ -24,6 +25,7 @@ export type GenerationFormValues = z.infer<typeof generationSchema>;
 interface UseGenerationFormOptions {
   onSuccess?: (generationId: string) => void;
   defaultValues?: Partial<GenerationFormValues>;
+  getEffectsChain?: () => EffectConfig[] | undefined;
 }
 
 export function useGenerationForm(options: UseGenerationFormOptions = {}) {
@@ -103,6 +105,7 @@ export function useGenerationForm(options: UseGenerationFormOptions = {}) {
       }
 
       const isQwen = engine === 'qwen';
+      const effectsChain = options.getEffectsChain?.();
       // This now returns immediately with status="generating"
       const result = await generation.mutateAsync({
         profile_id: selectedProfileId,
@@ -115,6 +118,7 @@ export function useGenerationForm(options: UseGenerationFormOptions = {}) {
         max_chunk_chars: maxChunkChars,
         crossfade_ms: crossfadeMs,
         normalize: normalizeAudio,
+        effects_chain: effectsChain?.length ? effectsChain : undefined,
       });
 
       // Track this generation for SSE status updates