Add Phase 1 foundation: Go module, core types, DB infrastructure, config

Establish the project foundation with three packages:
- core: shared types (Header, Metadata, Value, ObjectType, UUID generation)
- db: SQLite migration framework, connection management (WAL, FK, busy
  timeout), transaction helpers (StartTX/EndTX), time conversion
- config: runtime configuration (DB path, blob store, Minio, gRPC addr)

Includes initial schema migration (001_initial.sql) with 13 tables covering
shared infrastructure, bibliographic data, and artifact repository. Full test
coverage for all packages, strict linting (.golangci.yaml), and Makefile.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

db/db_test.go

@@ -0,0 +1,203 @@
+package db
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func tempDB(t *testing.T) string {
+	t.Helper()
+	dir := t.TempDir()
+	return filepath.Join(dir, "test.db")
+}
+
+func mustOpen(t *testing.T) *sql.DB {
+	t.Helper()
+	path := tempDB(t)
+	database, err := Open(path)
+	if err != nil {
+		t.Fatalf("Open failed: %v", err)
+	}
+	t.Cleanup(func() { _ = database.Close() })
+	return database
+}
+
+func mustOpenAndMigrate(t *testing.T) *sql.DB {
+	t.Helper()
+	database := mustOpen(t)
+	if err := Migrate(database); err != nil {
+		t.Fatalf("Migrate failed: %v", err)
+	}
+	return database
+}
+
+func TestOpenAndPing(t *testing.T) {
+	database := mustOpen(t)
+	if err := database.Ping(); err != nil {
+		t.Fatalf("Ping failed: %v", err)
+	}
+}
+
+func TestOpenCreatesFile(t *testing.T) {
+	path := tempDB(t)
+	database, err := Open(path)
+	if err != nil {
+		t.Fatalf("Open failed: %v", err)
+	}
+	t.Cleanup(func() { _ = database.Close() })
+
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		t.Fatal("database file was not created")
+	}
+}
+
+func TestMigrate(t *testing.T) {
+	database := mustOpenAndMigrate(t)
+
+	tables := []string{
+		"metadata", "tags", "categories", "publishers", "citations",
+		"authors", "artifacts", "artifact_tags", "artifact_categories",
+		"artifacts_history", "artifact_snapshots", "blobs", "schema_version",
+	}
+	for _, table := range tables {
+		var name string
+		row := database.QueryRow(`SELECT name FROM sqlite_master WHERE type='table' AND name=?`, table)
+		if err := row.Scan(&name); err != nil {
+			t.Errorf("table %q not found after migration: %v", table, err)
+		}
+	}
+}
+
+func TestMigrateIdempotent(t *testing.T) {
+	database := mustOpenAndMigrate(t)
+
+	if err := Migrate(database); err != nil {
+		t.Fatalf("second Migrate failed: %v", err)
+	}
+}
+
+func TestStartTXAndEndTX(t *testing.T) {
+	database := mustOpenAndMigrate(t)
+	ctx := context.Background()
+
+	tx, err := StartTX(ctx, database)
+	if err != nil {
+		t.Fatalf("StartTX failed: %v", err)
+	}
+
+	_, err = tx.ExecContext(ctx, `INSERT INTO tags (id, tag) VALUES ('test-id', 'test-tag')`)
+	if err != nil {
+		t.Fatalf("INSERT failed: %v", err)
+	}
+
+	if err := EndTX(tx, nil); err != nil {
+		t.Fatalf("EndTX (commit) failed: %v", err)
+	}
+
+	var tag string
+	row := database.QueryRow(`SELECT tag FROM tags WHERE id='test-id'`)
+	if err := row.Scan(&tag); err != nil {
+		t.Fatalf("committed row not found: %v", err)
+	}
+	if tag != "test-tag" {
+		t.Fatalf("expected 'test-tag', got %q", tag)
+	}
+}
+
+func TestEndTXRollback(t *testing.T) {
+	database := mustOpenAndMigrate(t)
+	ctx := context.Background()
+
+	tx, err := StartTX(ctx, database)
+	if err != nil {
+		t.Fatalf("StartTX failed: %v", err)
+	}
+
+	_, err = tx.ExecContext(ctx, `INSERT INTO tags (id, tag) VALUES ('rollback-id', 'rollback-tag')`)
+	if err != nil {
+		t.Fatalf("INSERT failed: %v", err)
+	}
+
+	simErr := context.DeadlineExceeded
+	if err := EndTX(tx, simErr); !errors.Is(err, simErr) {
+		t.Fatalf("EndTX should return the original error, got: %v", err)
+	}
+
+	var tag string
+	row := database.QueryRow(`SELECT tag FROM tags WHERE id='rollback-id'`)
+	if err := row.Scan(&tag); err == nil {
+		t.Fatal("rolled-back row should not be found")
+	}
+}
+
+func TestToDBTimeAndFromDBTime(t *testing.T) {
+	original := time.Date(2024, 6, 15, 14, 30, 0, 0, time.UTC)
+	s := ToDBTime(original)
+
+	if s != "2024-06-15 14:30:00" {
+		t.Fatalf("unexpected time string: %q", s)
+	}
+
+	parsed, err := FromDBTime(s, nil)
+	if err != nil {
+		t.Fatalf("FromDBTime failed: %v", err)
+	}
+
+	if !parsed.Equal(original) {
+		t.Fatalf("round-trip failed: got %v, want %v", parsed, original)
+	}
+}
+
+func TestFromDBTimeWithLocation(t *testing.T) {
+	s := "2024-06-15 14:30:00"
+	loc, err := time.LoadLocation("America/New_York")
+	if err != nil {
+		t.Skipf("timezone not available: %v", err)
+	}
+
+	parsed, err := FromDBTime(s, loc)
+	if err != nil {
+		t.Fatalf("FromDBTime failed: %v", err)
+	}
+
+	if parsed.Location() != loc {
+		t.Fatalf("expected location %v, got %v", loc, parsed.Location())
+	}
+}
+
+func TestFromDBTimeInvalid(t *testing.T) {
+	_, err := FromDBTime("not-a-date", nil)
+	if err == nil {
+		t.Fatal("expected error for invalid time string")
+	}
+}
+
+func TestForeignKeysEnabled(t *testing.T) {
+	database := mustOpen(t)
+
+	var fk int
+	row := database.QueryRow(`PRAGMA foreign_keys`)
+	if err := row.Scan(&fk); err != nil {
+		t.Fatalf("PRAGMA foreign_keys failed: %v", err)
+	}
+	if fk != 1 {
+		t.Fatalf("foreign keys should be enabled, got %d", fk)
+	}
+}
+
+func TestSchemaVersion(t *testing.T) {
+	database := mustOpenAndMigrate(t)
+
+	version, err := getCurrentVersion(database)
+	if err != nil {
+		t.Fatalf("getCurrentVersion failed: %v", err)
+	}
+	if version != 1 {
+		t.Fatalf("expected schema version 1, got %d", version)
+	}
+}