Set TTL to 0 for subdomains

[nt0xa]

In some of previous commits TTL for some records was set to 600 which breaks DNS notifications

[codecov]

Codecov Report

Merging #41 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #41   +/-   ##
=======================================
  Coverage   75.59%   75.59%           
=======================================
  Files          42       42           
  Lines        1639     1639           
=======================================
  Hits         1239     1239           
  Misses        273      273           
  Partials      127      127           

Impacted Files	Coverage Δ
internal/handlers/dnsx/static.go	79.31% <ø> (ø)

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