feat: v3 Go rewrite — full artifact proxy with web UI, TUI, and Terraform provider

Complete rewrite of ArtifactAPI from Python/FastAPI to Go as a single binary.

Core engine:
- 10 package providers: generic, docker, helm, pypi, npm, rpm, alpine,
  puppet, terraform, goproxy — each with built-in mutable patterns
- Content-addressable storage (SHA256 dedup across all remotes)
- Three-tier caching: Redis (TTL/locks) → S3/MinIO (blobs) → upstream
- Classifier with allowlist/blocklist per-remote (empty = allow all)
- Circuit breaker, conditional revalidation, stale-on-error
- Background garbage collection for orphaned blobs
- Access logging to PostgreSQL

API:
- v1 proxy endpoints (backwards compatible)
- v2 management API: CRUD remotes/virtuals, object browser, stats,
  health, SSE events, probe/test endpoint
- Virtual repos with index merging (Helm YAML + PyPI HTML)

Frontend (React + Vite, separate Dockerfile):
- Dashboard with stats, health indicators, top remotes
- Remotes list with type filter, remote detail with config/patterns
- Object browser with pagination and evict
- Test Remote page: probe any remote path, see headers/size/timing
- Virtuals page with expandable member lists

TUI (Bubble Tea):
- Dashboard, remotes list/detail, object browser, virtuals
- Vim-style navigation, artifactapi tui --endpoint <url>

Infrastructure:
- S3 client supports MinIO, Ceph RGW, AWS S3 (minio-go)
- PostgreSQL schema with migrations
- Docker Compose: API + UI + Postgres 17 + Redis 7 + MinIO
- Makefile with Go version check, build/test/lint/fmt/e2e targets
- Distroless Docker image (~15MB)

Testing:
- Unit tests for models, classifier, providers, mergers
- E2E tests with testcontainers-go (real Postgres/Redis/MinIO)

Terraform config:
- All 40 production remotes + helm virtual as HCL
- Provider repo: terraform-provider-artifactapi v0.0.1 (separate)

internal/api/v2/health.go

@@ -0,0 +1,43 @@
+package v2
+
+import (
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+
+	"git.unkin.net/unkin/artifactapi/internal/cache"
+	"git.unkin.net/unkin/artifactapi/internal/database"
+	"git.unkin.net/unkin/artifactapi/internal/storage"
+)
+
+type HealthHandler struct {
+	db    *database.DB
+	cache *cache.Redis
+	store *storage.S3
+}
+
+func NewHealthHandler(db *database.DB, c *cache.Redis, s *storage.S3) *HealthHandler {
+	return &HealthHandler{db: db, cache: c, store: s}
+}
+
+func (h *HealthHandler) Routes() chi.Router {
+	r := chi.NewRouter()
+	r.Get("/", h.health)
+	return r
+}
+
+func (h *HealthHandler) health(w http.ResponseWriter, r *http.Request) {
+	status := map[string]string{
+		"status":   "ok",
+		"postgres": "ok",
+		"redis":    "ok",
+		"s3":       "ok",
+	}
+
+	if err := h.db.Pool.Ping(r.Context()); err != nil {
+		status["postgres"] = "error"
+		status["status"] = "degraded"
+	}
+
+	writeJSON(w, http.StatusOK, status)
+}