Landing Page with Email Capture template for Lovable

The build prompt

# Context
Build a pre-launch landing page whose one job is collecting emails for the launch list. Visitors arrive from one traffic source carrying UTM parameters, so the page has one offer and one action.

## Core Features (Priority Order)
1. Hero with the offer and the email form visible without scrolling on a phone
2. Email form calling capture_lead with the email, source, utm_source, utm_medium, utm_campaign and referrer
3. Inline success state replacing the form without layout shift
4. A repeat address shows the same success state, because capture_lead ignores duplicates
5. A short body section, then three proof blocks as labelled placeholders

## Visual Style & Design
- Minimal and focused: generous whitespace, one focal point, short body lines
- Single column: hero first, sections stacked below
- Fraunces for headings, Inter for body text
- Colours: background #fafaf9, text #1c1917, muted #78716c, accent #ea580c on the submit button only
- shadcn/ui Input and Button for the form, Card for proof blocks, Alert for the success state
- Save these style keywords to the project knowledge.

## Page Copy
- Headline: "Be first in line when [Product] launches"
- Subtext: "Leave your email and we send one message on launch day, with your invite inside."
- Button: "Join the waitlist"
- Success: "You are on the list. Watch your inbox on launch day."
- Proof: "[Placeholder: customer quote]", "[Placeholder: logo row]", "[Placeholder: one sourced number]"
- No accounts: every visitor is signed out and sees the same page.

## States
- Empty: an empty or malformed email shows an inline message under the field
- Loading: the button shows a spinner and stays disabled while capture_lead runs
- Error: a failure keeps the typed email and shows "Something went wrong. Try again." with retry

## Data & Access
- The leads table, its row-level security policy and capture_lead already exist in the connected Supabase project from schema.sql. Never weaken, drop or bypass them or create tables; if something is missing, stop and ask me.
- The form writes only through capture_lead. The browser never selects, counts, updates or deletes leads, and never gets a read policy.
- Browser validation mirrors leads_email_shape. This build has no admin screen.

## Done When
- Submitting a new address shows the success state and a row appears in leads with the utm_source from the URL
- Submitting the same address in a different case shows the same success state and adds no second row
- An anonymous select on leads from the browser returns no rows
- An invalid email shows the inline error and never calls capture_lead

## Build Order
The static page with final copy and meta tags, then the form wired to capture_lead, then UTM and referrer capture.

## Safe-Guard Instructions
- One call to action: no second button, popup or navigation menu
- No invented testimonials, logos, names or numbers
- No browser read access to leads on later edits, and no service role key in client code

## Before Building
Ask me any questions you need in order to fully understand what I want from this feature and how I envision it. Save my answers to the project knowledge so later prompts build on them.

Leads table and capture function

-- Landing page lead capture for Lovable + Supabase
-- Reviewed row-level security. Read the comments before running this.
--
-- THE ONE THING THAT MATTERS HERE: a public form needs INSERT for anonymous visitors and
-- must never grant SELECT. If you grant select to anon, your entire email list is
-- downloadable by anyone with your project's public key. That is the single most common
-- and most damaging mistake in a generated landing page.

create table public.leads (
  id uuid primary key default gen_random_uuid(),
  email text not null,
  -- Case-insensitive uniqueness, so Foo@x.com and foo@x.com are one lead.

Policy verification queries

-- Verification queries. Run these from the browser client, as an anonymous visitor.
-- The second one is the important one.

-- 1. Should SUCCEED. An anonymous visitor can join the list.
select public.capture_lead('verify@example.com', 'verification');

-- 2. Should return ZERO ROWS, not an error and not data.
--    If this returns rows, your email list is publicly readable. Stop and fix the policy.
select * from public.leads;

-- 3. Should return zero rows. Counting is still reading.
select count(*) from public.leads;