initial commit: Artifacto v0.1

Self-hosted HTML artifact publisher. Single Go binary, SQLite metadata,
HTML on disk. Features: password-protected artifacts, per-artifact expiration,
admin dashboard with view metrics (privacy-preserving daily-salt visitor hash,
sparklines, 30-day SVG chart, top referrers), rate-limited unlock endpoint.

Packaged as a Docker image (two-stage, CGO_ENABLED=0, pure-Go SQLite).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.env.example

@@ -0,0 +1,3 @@
+ADMIN_PASSWORD=change-me
+SESSION_SECRET=generate-with-openssl-rand-hex-32
+BASE_URL=https://artifacto.hubris.network