release(1.3.0): add guard.enabled and keep form parsing working with body scanning on

[rennf93]

Closes #40

• version 1.2.0 to 1.3.0, install snippets and the docs status line to 1.3.0.
• Minor bump: guard.enabled is a new property (Add guard.enabled property to switch the auto-configuration off #38, default true, so existing apps see no change).
• Also ships the multipart and urlencoded form fix (Multipart upload loses its parts when detection body scanning is on #37): with body scanning on (the default), 1.2.0 apps lost multipart parts and @RequestParam form fields.
• Engine unchanged: guard-core 4.4.0 and the pinned engine ref stay as they are.
• CHANGELOG: Unreleased becomes [1.3.0] - 2026-10-17, and the hard-wrapped bullets of the pre-1.0.0 sections are now one line each (text unchanged).

Local gate: ./gradlew spotlessApply detekt build --no-daemon --max-workers=2 exit 0 with Redis on 6379 (58 tests, 0 failures), and no files changed by spotlessApply.