refactor(auth): E.44 — extract server-profile + lastfm + audio-settings factories (#609)

Three action-factories peel ~25 setters out of the authStore body,
following the playerStore action-factory pattern from Phase E:

- `createServerProfileActions` — `addServer`, `updateServer`,
  `removeServer` (the non-trivial one — drops every per-server map
  entry for the removed id), `setServers`, `setActiveServer`,
  `setLoggedIn`, `setConnecting`, `setConnectionError`, `logout`.
- `createAuthLastfmActions` — credentials + session connect/disconnect
  + error flag + master scrobbling toggle. Network calls (love /
  scrobble) stay in the playerStore-side `lastfmActions.ts`.
- `createAudioSettingsActions` — replay-gain / normalization /
  loudness mode toggles (each calls `usePlayerStore.getState()
  .updateReplayGainForCurrentTrack()` so a running track catches up),
  plus crossfade / gapless / hi-res / audio-output (no engine
  callback needed).

Pure code-move; no behaviour change. authStore.ts: 518 → 428 LOC (−90).

src/store/authAudioSettingsActions.ts

@@ -0,0 +1,74 @@
+import { clampStoredLoudnessPreAnalysisAttenuationRefDb } from '../utils/loudnessPreAnalysisSlider';
+import { DEFAULT_LOUDNESS_PRE_ANALYSIS_ATTENUATION_DB } from './authStoreDefaults';
+import { usePlayerStore } from './playerStore';
+import type { AuthState } from './authStoreTypes';
+
+type SetState = (
+  partial: Partial<AuthState> | ((state: AuthState) => Partial<AuthState>),
+) => void;
+
+/**
+ * Audio/playback settings. ReplayGain/normalization/loudness mode
+ * toggles call `usePlayerStore.getState().updateReplayGainForCurrentTrack()`
+ * so a running track's engine state catches up to the new mode without
+ * waiting for the next play. The plain crossfade/gapless/hi-res/output
+ * setters skip that — they don't change the gain state, only the
+ * neighbouring transitions or device routing.
+ */
+export function createAudioSettingsActions(set: SetState): Pick<
+  AuthState,
+  | 'setReplayGainEnabled'
+  | 'setNormalizationEngine'
+  | 'setLoudnessTargetLufs'
+  | 'setLoudnessPreAnalysisAttenuationDb'
+  | 'resetLoudnessPreAnalysisAttenuationDbDefault'
+  | 'setReplayGainMode'
+  | 'setReplayGainPreGainDb'
+  | 'setReplayGainFallbackDb'
+  | 'setCrossfadeEnabled'
+  | 'setCrossfadeSecs'
+  | 'setGaplessEnabled'
+  | 'setEnableHiRes'
+  | 'setAudioOutputDevice'
+> {
+  return {
+    setReplayGainEnabled: (v) => {
+      set({ replayGainEnabled: v });
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    },
+    setNormalizationEngine: (v) => {
+      set({ normalizationEngine: v });
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    },
+    setLoudnessTargetLufs: (v) => {
+      set({ loudnessTargetLufs: v });
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    },
+    setLoudnessPreAnalysisAttenuationDb: (v) => {
+      const n = typeof v === 'number' ? v : Number(v);
+      if (!Number.isFinite(n)) return;
+      set({ loudnessPreAnalysisAttenuationDb: clampStoredLoudnessPreAnalysisAttenuationRefDb(n) });
+    },
+    resetLoudnessPreAnalysisAttenuationDbDefault: () => {
+      set({ loudnessPreAnalysisAttenuationDb: DEFAULT_LOUDNESS_PRE_ANALYSIS_ATTENUATION_DB });
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    },
+    setReplayGainMode: (v) => {
+      set({ replayGainMode: v });
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    },
+    setReplayGainPreGainDb: (v) => {
+      set({ replayGainPreGainDb: v });
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    },
+    setReplayGainFallbackDb: (v) => {
+      set({ replayGainFallbackDb: v });
+      usePlayerStore.getState().updateReplayGainForCurrentTrack();
+    },
+    setCrossfadeEnabled: (v) => set({ crossfadeEnabled: v }),
+    setCrossfadeSecs: (v) => set({ crossfadeSecs: v }),
+    setGaplessEnabled: (v) => set({ gaplessEnabled: v }),
+    setEnableHiRes: (v) => set({ enableHiRes: v }),
+    setAudioOutputDevice: (v) => set({ audioOutputDevice: v }),
+  };
+}