fix(settings): use CIDR-aware proxy detection in ForwardedForHeaders setup check

[algojogacor]

Summary

Fixes #60287

The ForwardedForHeaders setup check used in_array($remoteAddress, $trustedProxies, true) to determine if the connecting proxy was trusted. This strict comparison cannot match CIDR ranges (e.g., 172.16.0.0/12) because the raw IP 172.21.0.7 and the CIDR string 172.16.0.0/12 are never equal.

Root Cause

ForwardedForHeaders.php line 75 used in_array() for exact string matching against the trusted proxies list. While getRemoteAddress() in Request.php correctly uses Symfony's IpUtils::checkIp() for CIDR-aware matching, the setup check did its own non-CIDR-aware comparison. This meant:

• The success message ("Your IP address was resolved as…") was never shown for CIDR-configured proxies
• The setup check was effectively blind to whether CIDR-based proxy detection was working

Fix

Replace the in_array()-based check with a direct comparison between $remoteAddress (raw REMOTE_ADDR) and $detectedRemoteAddress (from getRemoteAddress()). Since getRemoteAddress() already uses IpUtils::checkIp() internally for CIDR matching, this comparison correctly reflects whether proxy detection resolved a different client IP.

Added a test case for large /12 CIDR matching in RequestTest.php to prevent regressions.

Changes

• apps/settings/lib/SetupChecks/ForwardedForHeaders.php: Replace in_array() with direct address comparison (+12 -10 lines)
• tests/lib/AppFramework/Http/RequestTest.php: Add test case for /12 CIDR proxy detection (+9 -0 lines)

Testing

• CIDR /12 trusted proxy with valid X-Forwarded-For: Client IP resolved correctly ✅
• CIDR /24 trusted proxy (existing test preserved): Client IP resolved correctly ✅
• No trusted proxies configured: Falls through to success (no regression) ✅
• Trusted proxies configured but X-Forwarded-For missing: Warning shown correctly ✅