feat(intake): structured per-service intake questions

Services declare up to 8 intake fields (text/yesno, required) stored
as JSONB; shared/intake.go is the single normalization point — slug
keys, label/dup/unknown-key rules, yes/no canonicalization. Booking
create validates answers against the service declaration (missing
required -> 400), unknown keys are dropped before persist.

Answers surface on UpcomingBooking and CustomerBookingView; the
services page gains a compact editor and the public form renders
declared questions under contact details. Verified live end-to-end.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/migrations/00019_intake_fields.sql

@@ -0,0 +1,13 @@
+-- +goose Up
+-- Schema-light structured intake: services declare a small list of intake
+-- fields (key/label/type/required); bookings store the customer's answers as
+-- a JSON object keyed by the declared field keys. Both default to empty so
+-- existing services/bookings need no backfill.
+ALTER TABLE services
+  ADD COLUMN intake_fields jsonb NOT NULL DEFAULT '[]'::jsonb;
+ALTER TABLE bookings
+  ADD COLUMN intake jsonb NOT NULL DEFAULT '{}'::jsonb;
+
+-- +goose Down
+ALTER TABLE services DROP COLUMN IF EXISTS intake_fields;
+ALTER TABLE bookings DROP COLUMN IF EXISTS intake;