fix(matcher,plugin): case-insensitive matching, port accumulation, nil guards, doc comments

matcher: fix IPv6 normalization via netip.ParseAddr, port-range overwrite
by switching to []*PortRange map, case-insensitive domain/host matching,
glob.MustCompile→Compile to avoid panic on invalid patterns.

plugin: guard nil *Options in NewGRPCConn and NewHTTPClient; add
HTTPClientTransport helper for idle-connection cleanup.

net/*: add doc comments for all exported symbols (no code changes).

Add 30 tests (matcher_test.go 22, plugin_test.go 8) covering all
matcher types, nil safety, case insensitivity, IPv6 normalization,
port ranges, and plugin option composition.

internal/net/resovle.go

@@ -11,6 +11,9 @@ import (
 	ctxvalue "github.com/go-gost/x/ctx"
 )
 
+// Resolve resolves addr to a concrete IP address. If hosts is non-nil, it is
+// consulted first. If r is non-nil and no host mapping matched, the resolver
+// is used. If neither is available, addr is returned unchanged.
 func Resolve(ctx context.Context, network, addr string, r resolver.Resolver, hosts hosts.HostMapper, log logger.Logger) (string, error) {
 	if addr == "" {
 		return addr, nil