feat: Added heatmaps remote opt in

[benjackwhite]

Problem

Currently there is only a client side opt in for heatmaps

Changes

• Adds heatmaps_opt_in option
• Adds it to product analytics onboarding if enabled via flag

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Does this work well for both Cloud and self-hosted?

How did you test this code?

[posthog-bot]

📸 UI snapshots have been updated

2 snapshot changes in total. 0 added, 2 modified, 0 deleted:

• chromium: 0 added, 2 modified, 0 deleted (diff for shard 1)
• webkit: 0 added, 0 modified, 0 deleted

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[posthog-bot]

📸 UI snapshots have been updated

2 snapshot changes in total. 0 added, 2 modified, 0 deleted:

• chromium: 0 added, 2 modified, 0 deleted (diff for shard 1)
• webkit: 0 added, 0 modified, 0 deleted

Triggered by this commit.

👉 Review this PR's diff of snapshots.

[github-actions]

Size Change: +299 B (0%)

Total Size: 1.04 MB

ℹ️ View Unchanged

Filename	Size	Change
frontend/dist/toolbar.js	1.04 MB	+299 B (0%)

_{compressed-size-action}

[posthog-bot]

📸 UI snapshots have been updated

2 snapshot changes in total. 0 added, 2 modified, 0 deleted:

• chromium: 0 added, 2 modified, 0 deleted (diff for shard 1)
• webkit: 0 added, 0 modified, 0 deleted

Triggered by this commit.

👉 Review this PR's diff of snapshots.

[pauldambra]

didn't run it but LGTM

[neilkakkar]

backend looks good 👍