P1.1: Registry package with full CRUD and tests

SQLite schema (services, components, ports, volumes, cmd, events),
migrations, and complete CRUD operations. 7 tests covering:
idempotent migration, service CRUD, duplicate name rejection,
component CRUD with ports/volumes/cmd, composite PK enforcement,
cascade delete, and event insert/query/count/prune.

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

internal/registry/events.go

@@ -0,0 +1,96 @@
+package registry
+
+import (
+	"database/sql"
+	"fmt"
+	"time"
+)
+
+// Event represents a state-change event.
+type Event struct {
+	ID        int64
+	Service   string
+	Component string
+	PrevState string
+	NewState  string
+	Timestamp time.Time
+}
+
+// InsertEvent records a state transition.
+func InsertEvent(db *sql.DB, service, component, prevState, newState string) error {
+	_, err := db.Exec(
+		"INSERT INTO events (service, component, prev_state, new_state) VALUES (?, ?, ?, ?)",
+		service, component, prevState, newState,
+	)
+	if err != nil {
+		return fmt.Errorf("insert event %q/%q: %w", service, component, err)
+	}
+	return nil
+}
+
+// QueryEvents returns events for a service/component within a time window.
+// If service is empty, returns events for all services.
+// If component is empty, returns events for all components in the service.
+func QueryEvents(db *sql.DB, service, component string, since time.Time, limit int) ([]Event, error) {
+	query := "SELECT id, service, component, prev_state, new_state, timestamp FROM events WHERE timestamp > ?"
+	args := []any{since.UTC().Format("2006-01-02 15:04:05")}
+
+	if service != "" {
+		query += " AND service = ?"
+		args = append(args, service)
+	}
+	if component != "" {
+		query += " AND component = ?"
+		args = append(args, component)
+	}
+
+	query += " ORDER BY timestamp DESC"
+	if limit > 0 {
+		query += " LIMIT ?"
+		args = append(args, limit)
+	}
+
+	rows, err := db.Query(query, args...)
+	if err != nil {
+		return nil, fmt.Errorf("query events: %w", err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	var events []Event
+	for rows.Next() {
+		var e Event
+		var ts string
+		if err := rows.Scan(&e.ID, &e.Service, &e.Component, &e.PrevState, &e.NewState, &ts); err != nil {
+			return nil, fmt.Errorf("scan event: %w", err)
+		}
+		e.Timestamp, _ = time.Parse("2006-01-02 15:04:05", ts)
+		events = append(events, e)
+	}
+	return events, rows.Err()
+}
+
+// CountEvents counts events for a component within a time window matching
+// a specific new_state. Used for flap detection.
+func CountEvents(db *sql.DB, service, component string, since time.Time) (int, error) {
+	var count int
+	err := db.QueryRow(
+		"SELECT COUNT(*) FROM events WHERE service = ? AND component = ? AND timestamp > ?",
+		service, component, since.UTC().Format("2006-01-02 15:04:05"),
+	).Scan(&count)
+	if err != nil {
+		return 0, fmt.Errorf("count events %q/%q: %w", service, component, err)
+	}
+	return count, nil
+}
+
+// PruneEvents deletes events older than the given time.
+func PruneEvents(db *sql.DB, before time.Time) (int64, error) {
+	res, err := db.Exec(
+		"DELETE FROM events WHERE timestamp < ?",
+		before.UTC().Format("2006-01-02 15:04:05"),
+	)
+	if err != nil {
+		return 0, fmt.Errorf("prune events: %w", err)
+	}
+	return res.RowsAffected()
+}