Improve Solr connection error handling and improve HTML sanitization

[jguo144]

Description

Improves error handling for Solr connection failures and improve HTML sanitization in markdown rendering.

Changes

Search error handling

• Add SolrConnectionError exception type for connection-specific failures
• Detect Solr connection errors in PackageSearchQuery and raise appropriate exception
• Return 500 status with clear "Search Connection Error" message in API and dataset views
• Add test coverage for connection error scenarios

HTML sanitization

• Replace regex-based RE_MD_HTML_TAGS pattern with bleach_clean(strip=True)
• Ensures consistent and secure HTML stripping in markdown_extract() and render_markdown()
• Update test expectations to reflect improved sanitization behavior

Upstream Commits

• ckan@f6b032c
• ckan@6d0065f

[orca-security-us]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Secrets	0   0   0   0	View in Orca