feat(auth): store Subsonic API keys hashed; a new key is shown once (M462 #4983)

users.api_token held each user's apiKey in plaintext and was looked up by
equality, so a leaked row or backup handed out working keys. Migration
0063 replaces it with api_token_hash (sha256, hex), computed in place
from the existing keys so every Subsonic client keeps working.

The key can no longer be read back: GET /api/me/api-token is gone, and
POST returns the new key once. Settings shows it right after Regenerate
with a copy button and a "won't be shown again" note.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/api.go

@@ -108,7 +108,6 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 			authed.Put("/me/password", h.handleChangePassword)
 			authed.Put("/me/profile", h.handleUpdateMyProfile)
 			authed.Put("/me/timezone", h.handlePutTimezone)
-			authed.Get("/me/api-token", h.handleGetMyAPIToken)
 			authed.Post("/me/api-token", h.handleRegenerateMyAPIToken)
 			authed.Get("/me/sessions", h.handleListMySessions)
 			authed.Delete("/me/sessions/{id}", h.handleRevokeMySession)