[Apps] Update template Markdown spec

[rhart92]

Description

Attribution

• Custom agent: Coder
• Custom agent created by: Ryan Hart (ryan@makenotion.com)
• Custom agent requested by: Ryan Hart (ryan@makenotion.com)
• Notion thread: View thread

Update the app templates used by ntn apps new to current Notion Markdown, including database resource mentions and Perfect Meetings help. Update the canonical app instructions and regenerate both template copies.

How was this change tested?

• Automated test (unit, integration, etc.)
• Manual test (built and deployed the default template locally; validated both templates' Markdown with the merged server parser)

Perfect Meetings was deployed locally with a temporary Calendar SDK compatibility patch that is not included in this PR. Its deployed Markdown matches this branch. Checked the embedded custom view, database links, expanded help toggle, and rendered agent instructions; server readback confirmed mention annotations, a toggle block, and the persisted instruction page. Markdown and formatting checks passed.

Local provisioning returned no Markdown errors. A strict-parser negative check rejected <mention-page> with an error naming the unsupported tag.

Perfect Meetings' final-branch typecheck/build remains blocked by existing Calendar SDK incompatibilities. Update its Calendar API usage separately before redeploying; Calendar sync and research execution also require account setup.

Local deployment screenshots (after-only)

Is this feature gated? (Optional)

• Yes (private-alpha Apps)
• No