Web dashboard step 1: migration, sessions, users CLI, public site

Migration 0004 (users, sessions, config_changes, profile_versions, jobs,
rating_events.user_id, runs.report_json, issues.issue_json), the issue
snapshot writer and loader, the web module skeleton with layout and static
assets, axum-login/tower-sessions over a sqlx session store, password-auth
users with a CLI, the login throttle, the origin check, security headers,
and the public issue pages, archive, Atom feed and robots.txt.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NHyYupFdBiR4VfoUM7NjSM

src/web/templates/login.html

@@ -0,0 +1 @@
+{% extends "layout.html" %}{% block content %}<section class="reading narrow"><h1>Sign in</h1>{% if !error.is_empty() %}<p class="error">{{ error }}</p>{% endif %}<form method="post" action="/login"><input type="hidden" name="next" value="{{ next }}"><label>Username <input name="username" autocomplete="username" required></label><label>Password <input type="password" name="password" autocomplete="current-password" required></label><button type="submit">Sign in</button></form></section>{% endblock %}