Hello Bar

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Build me an announcement bar that replaces Hello Bar: one message at the top of my site, shown to the right people, that does not follow anybody around.

STACK
- Node 20+ with Fastify, SQLite through better-sqlite3
- One embeddable script under 6KB gzipped, from my own domain
- Server-rendered admin
- Caddy in front

THE DATA MODEL
- bars: id, name, kind, status, message_md, cta_label, cta_url, theme_json, position, priority, created_at
- targeting: id, bar_id, rule_kind, operator, value — url pattern, referrer, country, device, first visit, returning, utm parameter, date range
- schedules: id, bar_id, starts_at, ends_at, weekdays_json, hours_json
- impressions: id, bar_id, session_hash, shown_at, clicked_at, dismissed_at, converted_at
- captures: id, bar_id, email, session_hash, created_at — when the bar collects an address
- Kinds: bar, ribbon, slide-in, modal. The modal exists because people ask for it, and the admin says out loud that it converts better and annoys more

THE BAR ITSELF
- A strip at the top or bottom, pushing the page down rather than covering it — a bar that hides a site's own navigation is a bar that gets removed
- One message, one action, one dismiss control. No second line of copy, no image, no countdown unless the countdown is real
- A countdown must end at a real time and, when it ends, the bar goes. A timer that resets per visitor is a lie with a clock on it
- Dismissal is remembered for N days, per bar, in localStorage plus a server-side session hash — a dismissed bar that returns on the next page is the single most hated pattern on the web
- Renders from one JSON payload fetched once per session; no layout shift after paint because the space is reserved from the first frame

TARGETING
- By page, by referrer, by country, by device, by first-or-returning visit, by UTM parameter, by date and time of day
- Rules read as sentences in the admin: 'on the pricing page, for visitors from search, on desktop, this week'
- Only one bar shows at a time, chosen by priority; the admin shows which rules would collide before saving
- A preview mode only the admin sees, driven by a query parameter

WHAT IT COLLECTS
- Optionally an email address, with the same care as anywhere else: double opt-in off by default but available, a stored consent sentence, and a one-click unsubscribe that needs no login
- Never a phone number, never a name, unless the owner adds the field deliberately
- Addresses exportable and deletable by address

MEASURING
- Impressions, clicks, dismissals, captures, per bar and per rule
- Click-through and capture rate, both defined on the page
- A/B two messages on one bar, split by session hash, with the split and the sample size shown — and no winner declared before the number of impressions the admin set
- Bots excluded from published figures and recorded with a flag

PRIVACY
- No cookie, no cross-site identifier, no third-party request
- Country from a local database file
- The session hash is salted and never leaves the server in a form that can be joined to anything

THE INTERFACE
- One page per bar: the message, the rules, the schedule, and a live preview at three widths
- A list showing which bar is live where, right now
- Dark and light, one accent

OPERATIONS
- .env: DATABASE_PATH, BASE_URL, HASH_SALT, ALLOWED_ORIGINS, SMTP_URL
- Migrations on boot, each once
- Payload endpoint from memory with an ETag: it is hit by every page view of the host site
- Nightly backup off the machine, restore script
- Health endpoint

WHAT MATTERS MOST
The dismissal memory and the no-layout-shift rendering. Build those first and put a bar on a real site for a day. If a dismissed bar comes back, or the page jumps when it loads, nothing else about the tool matters.

Give me the repository, the embeddable script, migrations, .env.example, a seed with two bars and colliding rules, and a README with deploy steps behind Caddy.