Adds a client-side status filter (All / Active / Inactive / No
connection) to the Providers page, applied over the already-fetched
provider + connection list. Status derives from getProviderStats
(total, allDisabled); noAuth providers count as Active. Filter composes
with the existing search across all provider sections. Part of #3699.
Closes four SSRF guard bypasses reported in #3714:
- Block alternate IPv6 encodings (hex format, NAT64, IPv4-compatible, IPv4-mapped) by parsing to 16-bit groups
- Normalize trailing dots on hostnames to prevent FQDN bypasses
- Add assertPublicUrlResolved() with DNS resolution to block wildcard DNS domains resolving to private/metadata IPs
- Add fetchPublic() to safely handle and validate HTTP redirects