Splash screen: [web] port, IP address only (M7)

[txoof-bot]

Closes #242

What changed

• splash_screen gets a setting port (default 8080, 1–65535) and uses it in both web addresses and in the QR code. The fixed WEB_PORT constant is gone.
• Scheduler: the built-in splash is built with port = [web] port from the config at start. Like the web interface itself ([web] port is in WEB_NEXT_START), a changed port applies at the next start of PaperPi, so the splash never shows a port the web interface isn't using.
• A splash that a user adds to the rotation with a [[plugin]] block uses its own port setting (default 8080); the README says so.
• The host-name line is gone (txoof, 2026-10-07: "keep it simple"): the web interface only accepts IP addresses, so http://<name>.local:8080 led to an error page. The splash now shows the IP address (larger) and the QR code; the host-name reader is removed.
• Plugin README updated.

Why: #236 used a fixed 8080 because [web] port did not exist yet when it was built; it arrived with M5 part 1 (#239/#240). With another port, the splash and its QR code pointed to the wrong address.

Size: +88/−107 (git diff --shortstat origin/main...HEAD). Small on purpose: txoof asked for this fix as its own PR.

Reference images for the splash changed (one address line instead of two).

Area

plugins/splash_screen, the splash part of src/paperpi/scheduler.py, their tests. Checked: open PR #241 (M5 part 2a) also changes scheduler.py, but other lines.

Tests

• splash_screen: the default port equals [web] port's default; with port = 9000 both addresses and the QR code use 9000.
• splash_screen: port must be a whole number 1–65535 (0, 65536 and text are refused).
• scheduler: the splash update gets [web] port, and keeps it after reloads (also when it draws again after a rotation change).
• uv run pytest passes (1151 passed, 1 deselected; fewer because the host-name tests are gone)
• uv run ruff check . passes
• Hardware tests: not needed

Review

• Review agents' comments answered (one combined comment)

Only txoof approves and merges this PR.

🤖 Generated with Claude Code

[txoof-bot]

Answers to the review

One review agent did all four reviews (code, tests, security, docs), since the PR is small.

1. Blocking: after a reload the splash showed a port the web interface isn't using. [web] port only changes at the next start (WEB_NEXT_START; the web server keeps its port). Fixed: the scheduler keeps the port from the start; the reload test now expects the old port, also when the splash draws again after a rotation change. README updated.
2. A splash added to the rotation by the user shows its own port (default 8080), not [web] port. Kept as it is: it is not what the plugin is meant for, and the README says so.
3. The plugin's port accepted text ([web] port is strict). Fixed: strict=True; test for 0, 65536 and text.
4. The host-name address (http://paperpi.local:PORT) can't be opened: the web interface only accepts an IP address or localhost. Not caused by this PR; asking txoof how to handle it (follow-up).

Security: nothing found. Tests: 3 of 4 planted bugs were caught; the 4th (port range) now has a test.