chore: add frame-ancestors directive to CSP header

[markphelps]

Fixes: FLI-190

Adds missing frame-ancestors directive to Content-Security-Policy response header to prevent clickjacking

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-ancestors

[codecov-commenter]

Codecov Report

Merging #1317 (2e7070b) into main (0af41e9) will increase coverage by 0.09%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main    #1317      +/-   ##
==========================================
+ Coverage   80.37%   80.46%   +0.09%     
==========================================
  Files          43       43              
  Lines        3307     3307              
==========================================
+ Hits         2658     2661       +3     
+ Misses        518      516       -2     
+ Partials      131      130       -1     

Impacted Files	Coverage Δ
internal/server/flag.go	81.92% <100.00%> (+3.61%)	⬆️
internal/server/rule.go	76.92% <100.00%> (+3.84%)	⬆️
internal/server/segment.go	79.16% <100.00%> (+4.16%)	⬆️
internal/storage/oplock/sql/sql.go	90.82% <0.00%> (-5.51%)	⬇️

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[GeorgeMac]

Nice 🔒