add Japanese translation for tickets module documentation

[tah5882]

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Pull request overview

Adds a Japanese documentation page for the Tickets module.

Changes:

• Introduces a new Japanese MDX doc for the Tickets module under i18n/ja/....
• Adds localized front matter (title/description/keywords) and translates the initial sections (Overview → Form Settings).

Comments suppressed due to low confidence (1)

i18n/ja/docusaurus-plugin-content-docs/current/modules/tickets.mdx:131

• The document ends mid-sentence and contains a dangling escaped bold marker (\*\*) at the end, which will render incorrectly and likely indicates missing content (the rest of the "Panel Messages" section and subsequent sections). Please complete the translation and remove the stray/unclosed markdown emphasis so the page renders cleanly.

### パネルメッセージ (Panel Messages)

チケットのライフサイクルのさまざまなイベントで送信されるメッセージをカスタマイズします。各メッセージは、プレーンテキスト、または色、作成者、タイトル、説明、画像を含む \*\*

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