Update compat bounds and remove stale docs/registry.md

[ViralBShah]

Summary

• Tighten compat: HTTP "0.6, 1" → "1", CodecZlib "0.5, 0.6, 0.7" → "0.7"
• Set minimum julia compat to "1.6" (was "0.7, 1")
• Simplify stdlib compat entries (drop 0.7 ranges, keep <0.0.1 for Julia 1.6)
• Use 'min' instead of hardcoded '1.6' in CI test matrix
• Drop stale HTTP = "0.9, 1" compat from docs/Project.toml
• Remove checked-in docs/registry.md — it's auto-generated into docs/src/registry.md (already gitignored) and the stale copy had broken http:/// URLs

Note: Julia 1.6 min jobs fail in the Integration test due to latest ImageIO dropping Julia 1.6 support (neither save nor fileio_save is defined). This is a pre-existing issue unrelated to this PR.

Test plan

• CI passes on Julia 1, lts, nightly
• Docs build succeeds
• Julia min (1.6) — known failure in Integration test (ImageIO incompatibility)

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.31%. Comparing base (70fe308) to head (0562021).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #435   +/-   ##
=======================================
  Coverage   91.31%   91.31%           
=======================================
  Files          11       11           
  Lines         714      714           
=======================================
  Hits          652      652           
  Misses         62       62           

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