fix: show booking answers in host emails

[harley]

Summary

Hosts now see a guest's saved intake responses in new-booking and reassignment emails. The responses were stored before, but the notifications omitted them.

Risks

Guest-provided text now appears in email to assigned hosts. HTML escapes that text, and attendee confirmations do not include it. If loading responses fails, the email still sends without them and logs the error.

Validation

• make build and go test ./... passed on this branch.
• Rendered a sample host email in Chromium and checked multiline answers and layout.

[github-actions]

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[pullfrog]

ℹ️ No critical issues — one coverage nit below.

Reviewed changes

• Host email templates — BookingData.Answers ([]BookingAnswer{Label,Value}) renders in the host plain-text and HTML confirmations only; the attendee templates don't reference it, so no leak path.
• Answer loading — new bookingAnswersForEmail joins booking_answers to event_type_questions, ordered by question position, mirroring the existing admin GetBookingAnswers query.
• Wiring — invoked at the two host-notify sites: dispatchBookingConfirmation (shared by REST + MCP) and reassign.go, with failures logged and the email still sent.
• Tests — unit test pins host-only inclusion plus HTML escaping; integration test pins end-to-end host email content.

Verified: both new tests pass, go test ./internal/mailer/ ./internal/handler/ is green, and go vet / gofmt are clean. HTML is auto-escaped by html/template while the plain-text path correctly does not escape; the inner join is safe because booking_answers.question_id is ON DELETE CASCADE (migration 00014).

ℹ️ Nitpicks

• The reassignment call site (internal/handler/reassign.go:216) is the second use of the new helper but has no test asserting answers reach the reassigned host, while the create path is covered end-to-end. Optional, but a small reassign-email assertion would close the gap.

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[harley]

The reassignment call site ... has no test asserting answers reach the reassigned host.

Added that assertion in f9d2e5d. It checks the saved answer in both the new host's plain-text and HTML email. go test ./... passes.

[pullfrog]

✅ No new issues found.

Reviewed changes

• Reassignment email coverage — TestReassignBooking_movesHost now seeds a question and answer, then waits for the email to the new host and asserts both label and value appear in text and HTML. It would fail without the reassign.go:216 wiring, so it genuinely closes the prior review's coverage nitpick.

Verified: go test ./internal/handler/ passes, and the incremental delta is test-only — no production behavior changed since the prior review.

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