Fix incomplete IPv6 regex patterns for compressed addresses

[Copilot]

The IPv6 regex patterns failed to match valid compressed addresses when :: appears mid-address with multiple segments on both sides (e.g., fe80:1:2::3:4:5:6).

Changes

• Comprehensive compression handling: Added patterns for all valid :: positions (1-6 groups before, 1-6 groups after) instead of the previous limited set
• Pattern ordering: Reordered alternatives from most-to-least specific to prevent premature partial matches (e.g., 2001:db8:: matching when input is 2001:db8::1)
• Consistency: Updated both bracketed [IPv6] and non-bracketed patterns

Implementation

The fix enumerates all valid IPv6 compression positions. For example:

// Old: Only matched specific compression patterns
"(?:[0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}" // Incomplete

// New: Handles all compression positions
"(?:[0-9a-fA-F]{1,4}:){6}:[0-9a-fA-F]{1,4}|"      // 6 groups :: 1 group
"(?:[0-9a-fA-F]{1,4}:){5}:(?:[0-9a-fA-F]{1,4}:)?[0-9a-fA-F]{1,4}|" // 5 :: 1-2
"(?:[0-9a-fA-F]{1,4}:){4}:(?:[0-9a-fA-F]{1,4}:){0,2}[0-9a-fA-F]{1,4}|" // 4 :: 1-3
// ... (continues for all valid combinations)

Note: In (?:[0-9a-fA-F]{1,4}:){6}:, the quantified group already includes trailing colons (matching a:b:c:d:e:f:), so a single : suffix correctly produces ::.

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