Feat/v3 go rewrite (#47)

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)

---------

Co-authored-by: Ben Vincent <ben@unkin.net>
Reviewed-on: #47

cmd/artifactapi/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"git.unkin.net/unkin/artifactapi/internal/config"
+	"git.unkin.net/unkin/artifactapi/internal/server"
+	"git.unkin.net/unkin/artifactapi/internal/tui"
+)
+
+func main() {
+	if len(os.Args) > 1 && os.Args[1] == "tui" {
+		endpoint := os.Getenv("ARTIFACTAPI_ENDPOINT")
+		if endpoint == "" {
+			endpoint = "http://localhost:8000"
+		}
+		for i, arg := range os.Args {
+			if arg == "--endpoint" && i+1 < len(os.Args) {
+				endpoint = os.Args[i+1]
+			}
+		}
+
+		app := tui.New(endpoint)
+		if err := app.Run(); err != nil {
+			fmt.Fprintf(os.Stderr, "tui error: %v\n", err)
+			os.Exit(1)
+		}
+		return
+	}
+
+	cfg, err := config.Load()
+	if err != nil {
+		slog.Error("failed to load config", "error", err)
+		os.Exit(1)
+	}
+
+	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer cancel()
+
+	srv, err := server.New(cfg)
+	if err != nil {
+		slog.Error("failed to create server", "error", err)
+		os.Exit(1)
+	}
+
+	if err := srv.Run(ctx); err != nil {
+		slog.Error("server exited with error", "error", err)
+		os.Exit(1)
+	}
+}