feat: add authentication, audit log, HTTP API and base web UI

Phase 1 foundation. Local auth per ADR-0006: Argon2id passwords, opaque
hashed session tokens with idle/absolute expiry, CSRF token plus Origin
check on cookie sessions, per-IP token bucket and per-account exponential
lockout, three roles enforced by middleware, personal API tokens for
noemactl. Audit log writer used by every admin mutation.

API: request ids, panic recovery, strict CSP and security headers, body
limits, single JSON error envelope, health/ready/status, users, sessions,
tokens, audit, token-protected /metrics.

UI: embedded html/template pages (login, first-run setup, dashboard,
system, users, account, audit, interpretation boundary), light/dark
theme, dependency-free app.js with CSRF-aware fetch and SSE helper.

Binaries: noemad with graceful shutdown, migrations at start, bootstrap
admin from environment, supervised background tasks; noemactl with
status, migrate, user create and meaningful exit codes.

CHANGELOG.md

@@ -5,4 +5,5 @@ All notable changes to Noema are recorded here. Format follows Keep a Changelog;
 ## [Unreleased]
 
 ### Added
+- Phase 1 foundation: configuration, structured logging, metrics, migrations, local authentication (Argon2id, sessions, CSRF, lockout, roles, API tokens), audit log, JSON API skeleton, server-rendered admin UI with light/dark theme, `noemad` and `noemactl`.
 - Repository foundation: plan, architecture, security model, threat model, ADRs, Makefile, container files.