fix(connectors): meilisearch_sink URL scheme check is case-sensitive

[mattp5657]

Which issue does this PR address?

Closes #4157

What changed?

normalize_host detected the URL scheme via a literal starts_with("http://")/starts_with("https://") check. An uppercase or mixed-case scheme like HTTPS://host matched neither literal, fell through to the "no scheme" branch, and got http:// prepended, producing http://HTTPS://host, which parses as scheme="http", host="https", silently connecting to the wrong host over plaintext.

Scheme detection is now case-insensitive (eq_ignore_ascii_case on the split-off scheme), matching opensearch_sink's existing pattern. An unsupported scheme (e.g. ftp://) is now also rejected outright instead of being silently mangled the same way.

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

Claude was used in creating this PR.

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[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 30.65%. Comparing base (78151b9) to head (d2e646b).

Files with missing lines	Patch %	Lines
core/connectors/sinks/meilisearch_sink/src/lib.rs	93.75%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #4158       +/-   ##
=============================================
- Coverage     87.13%   30.65%   -56.49%     
  Complexity     1455     1455               
=============================================
  Files          1273     1270        -3     
  Lines        215301   173708    -41593     
  Branches     179911   138909    -41002     
=============================================
- Hits         187611    53244   -134367     
- Misses        23173   118447    +95274     
+ Partials       4517     2017     -2500     

Components	Coverage Δ
Rust Core	16.69% <93.75%> (-71.48%)	⬇️
Java SDK	67.58% <ø> (ø)
C# SDK	76.97% <ø> (-0.16%)	⬇️
Python SDK	91.34% <ø> (+0.37%)	⬆️
PHP SDK	85.65% <ø> (-0.03%)	⬇️
Node SDK	96.17% <ø> (-0.06%)	⬇️
Go SDK	69.40% <ø> (-0.05%)	⬇️

Files with missing lines	Coverage Δ
core/connectors/sinks/meilisearch_sink/src/lib.rs	74.15% <93.75%> (+0.89%)	⬆️

... and 689 files with indirect coverage changes

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