refactor: migrate data-fetching sagas to hooks / TanStack Query

[dylanjeffers]

Summary

Move pure data-fetch and localStorage-persistence side effects out of sagas and into React hooks where TanStack Query already lives. Five sagas are deleted; share-modal is trimmed to a 22-line saga that only flips modal visibility (data loading now happens in useShareContent via useTrack/useUser/useCollection).

• cookieBanner — useEffect in WebPlayer checks shouldShowCookieBanner; CookieBanner calls the gdpr util directly on dismiss.
• playback rate — new usePlaybackRatePersistence hook hydrates from localStorage on mount and persists on change.
• remote-config — useEffect calls remoteConfigInstance.waitForRemoteConfig() then dispatches setDidLoad.
• share-modal — slice now stores the request payload (type + IDs); useShareContent derives ShareContent from cached useTrack/useUser/useCollection. Modal opens immediately (vs. waiting for saga fetch); existing null guards already cover the brief loading window.
• playback-position — usePlaybackPositionPersistence handles hydration (incl. legacy-key migration) + localStorage persistence; usePlaybackPositionPolling drives the 1s resume-position loop on web only.

userListModal was on the original audit list but turned out to be pure action routing with no data fetching — not actually a TanStack Query candidate — so it was left as-is.

Drive-by

Removed an unused isMobile prop on the named CookieBanner export in DownloadPage.tsx. The CookieBanner uses useIsMobile() internally so the prop was dead, but it was being masked by a stale @ts-ignore on the next line. Fixing the dismiss callback's return type let TypeScript catch the excess prop.

Stats

27 files changed, ~415 / -367 lines. 4 saga files deleted, 5 new hook files added.

Test plan

• Sign in, play a long-form track, verify resume position survives reload (playback-position polling + persistence)
• Change playback rate, reload page/app, verify rate persists (playback rate)
• Open share modal from a track / playlist / profile, verify content populates and share/copy-link actions work (share-modal + useShareContent)
• Cold-load on web; gated feature flags should resolve once remote config loads (remote-config didLoad)
• EU prod: cookie banner appears and dismiss persists (cookieBanner) — hard to verify locally
• iOS + Android: playback rate + position persistence still work
• npm run typecheck passes for common, web, mobile (verified locally)

🤖 Generated with Claude Code

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