feat(G304): add os.Root remediation hint (Autofix) when Go >= 1.24

[eshentials]

Description

What
Closes #1297
Adds an Autofix suggestion to G304 issues recommending use of os.Root for path-scoped file operations when Go version >= 1.24.
The hint appears on flagged cases (unsafe Join, unresolved path identifiers, string concatenation in paths) and is gated by Go version.

Why
os.Root (Go 1.24+) constrains file operations under a fixed root and prevents directory/symlink traversal by design.
This gives developers a modern and more robust remediation path versus ad-hoc path sanitization alone.

How
Introduces osRootSuggestion() in rules/readfile.go, checks Go version via existing gosec.GoVersion(), and attaches the suggestion via Issue.Autofix when applicable.
No change to detection logic or severity; purely an advisory hint.
Examples (suggestion appears with G304)
os.OpenFile(filepath.Join(base, userInput), ...) when not paired with filepath.Clean
Unresolved path identifiers passed to os.Open/OpenFile/ReadFile
Binary path concatenations

Compatibility
Suggestion only shown for Go >= 1.24 (some Root methods land in 1.25).
Zero behavioral changes to rule triggering; tests remain green.

Tests
go test ./rules -v: 42 passed, 0 failed.

[eshentials]

@ccojocar pls check

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 76.92308% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.31%. Comparing base (1216c9b) to head (3470cd3).
⚠️ Report is 104 commits behind head on master.

Files with missing lines	Patch %	Lines
rules/readfile.go	76.92%	6 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1386      +/-   ##
==========================================
- Coverage   68.49%   63.31%   -5.19%     
==========================================
  Files          75       74       -1     
  Lines        4384     5286     +902     
==========================================
+ Hits         3003     3347     +344     
- Misses       1233     1805     +572     
+ Partials      148      134      -14     

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