Added comprehensive tests for 6 previously untested pure utility functions:
- sortContent: sorts comma-separated storage content values
- formatSeconds: converts total seconds to HH:MM:SS format
- dedupeStringsPreserveOrder: deduplicates strings while preserving order
- sanitizeGuestAddressStrings: validates and filters IP addresses
- copyFloatPointer: creates independent copy of float64 pointer
- clampInterval: clamps time.Duration to specified bounds
Tests cover edge cases including empty inputs, boundary conditions,
special values (DHCP, loopback addresses), and various separators.
Coverage increased from 36.8% to 37.5%.
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