Release 3.1.3

What's Changed

🐛 Bug Fixes

• Only mark an invoice paid once API and MCP payments settle it by @pierredup in #3075
• Flatten nested objects before handing log records to frankenphp_log() by @pierredup in #3095
• Leave the brotli extension out of the static PHP build by @pierredup in #3116
• Fix template heading to show title and add buttons by @pierredup in #3120

🔧 Other Changes

• Date the 3.1.2 changelog entry and add its UPGRADE.md notes by @pierredup in #3066
• Harden create_release.sh: merge-up conflict must not swallow the next-patch milestone by @pierredup in #3067
• Add the four missing snapcraft metadata fields by @pierredup in #3068
• SOL-548: Document that the non-final carve-out covers embeddables by @pierredup in #3071
• Chart each month once in the revenue chart at month end by @pierredup in #3098
• Add least-privilege permissions block to security-checker.yml by @pierredup in #3115
• Bump locked Symfony to v8.1.11 on 3.1.x to clear 12 advisories by @pierredup in #3114
• Fix PostgreSQL-order-dependent getReminderHistory() tie on sentAt (SOL-578) by @pierredup in #3111
• Batch-load onboarding progress to eliminate N+1 in dispatch cron by @seer-by-sentry[bot] in #3080

Full Changelog: 3.1.2...3.1.3