chore: CSP script nonces, deploy health check, dead-code cleanup

Add per-request CSP nonces (drop script unsafe-inline), post-deploy /api/health gate, bump next-auth to beta.32, and remove unused motion/cache/permission helpers.

Co-authored-by: Cursor <[email protected]>

package.json

@@ -49,7 +49,7 @@
 		"music-metadata": "^11.14.0",
 		"mysql2": "^3.23.0",
 		"next": "^16.2.11",
-		"next-auth": "5.0.0-beta.31",
+		"next-auth": "5.0.0-beta.32",
 		"next-intl": "^4.13.3",
 		"next-view-transitions": "^0.3.5",
 		"nodemailer": "^7.0.13",