Add master database with nodes, placements, and edge_routes

New internal/masterdb/ package for mcp-master cluster state. Separate
from the agent's registry because the schemas are fundamentally
different (cluster-wide placement vs node-local containers).

Tables: nodes, placements, edge_routes. Full CRUD with tests.
Follows the same Open/migrate pattern as internal/registry/.

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

internal/masterdb/edge_routes.go

@@ -0,0 +1,95 @@
+package masterdb
+
+import (
+	"database/sql"
+	"fmt"
+	"time"
+)
+
+// EdgeRoute records a public route managed by the master.
+type EdgeRoute struct {
+	Hostname        string
+	ServiceName     string
+	EdgeNode        string
+	BackendHostname string
+	BackendPort     int
+	CreatedAt       time.Time
+}
+
+// CreateEdgeRoute inserts or replaces an edge route record.
+func CreateEdgeRoute(db *sql.DB, hostname, serviceName, edgeNode, backendHostname string, backendPort int) error {
+	_, err := db.Exec(`
+		INSERT INTO edge_routes (hostname, service_name, edge_node, backend_hostname, backend_port, created_at)
+		VALUES (?, ?, ?, ?, ?, datetime('now'))
+		ON CONFLICT(hostname) DO UPDATE SET
+			service_name = excluded.service_name,
+			edge_node = excluded.edge_node,
+			backend_hostname = excluded.backend_hostname,
+			backend_port = excluded.backend_port
+	`, hostname, serviceName, edgeNode, backendHostname, backendPort)
+	if err != nil {
+		return fmt.Errorf("create edge route %s: %w", hostname, err)
+	}
+	return nil
+}
+
+// ListEdgeRoutes returns all edge routes.
+func ListEdgeRoutes(db *sql.DB) ([]*EdgeRoute, error) {
+	return queryEdgeRoutes(db, `SELECT hostname, service_name, edge_node, backend_hostname, backend_port, created_at FROM edge_routes ORDER BY hostname`)
+}
+
+// ListEdgeRoutesForService returns edge routes for a specific service.
+func ListEdgeRoutesForService(db *sql.DB, serviceName string) ([]*EdgeRoute, error) {
+	rows, err := db.Query(`
+		SELECT hostname, service_name, edge_node, backend_hostname, backend_port, created_at
+		FROM edge_routes WHERE service_name = ? ORDER BY hostname
+	`, serviceName)
+	if err != nil {
+		return nil, fmt.Errorf("list edge routes for %s: %w", serviceName, err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	return scanEdgeRoutes(rows)
+}
+
+// DeleteEdgeRoute removes a single edge route by hostname.
+func DeleteEdgeRoute(db *sql.DB, hostname string) error {
+	_, err := db.Exec(`DELETE FROM edge_routes WHERE hostname = ?`, hostname)
+	if err != nil {
+		return fmt.Errorf("delete edge route %s: %w", hostname, err)
+	}
+	return nil
+}
+
+// DeleteEdgeRoutesForService removes all edge routes for a service.
+func DeleteEdgeRoutesForService(db *sql.DB, serviceName string) error {
+	_, err := db.Exec(`DELETE FROM edge_routes WHERE service_name = ?`, serviceName)
+	if err != nil {
+		return fmt.Errorf("delete edge routes for %s: %w", serviceName, err)
+	}
+	return nil
+}
+
+func queryEdgeRoutes(db *sql.DB, query string) ([]*EdgeRoute, error) {
+	rows, err := db.Query(query)
+	if err != nil {
+		return nil, fmt.Errorf("query edge routes: %w", err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	return scanEdgeRoutes(rows)
+}
+
+func scanEdgeRoutes(rows *sql.Rows) ([]*EdgeRoute, error) {
+	var routes []*EdgeRoute
+	for rows.Next() {
+		var r EdgeRoute
+		var createdAt string
+		if err := rows.Scan(&r.Hostname, &r.ServiceName, &r.EdgeNode, &r.BackendHostname, &r.BackendPort, &createdAt); err != nil {
+			return nil, fmt.Errorf("scan edge route: %w", err)
+		}
+		r.CreatedAt, _ = time.Parse("2006-01-02 15:04:05", createdAt)
+		routes = append(routes, &r)
+	}
+	return routes, rows.Err()
+}