feat(infra): sqlite_apply_versioned_migrations + dedup fn_operations + registry

Promueve patron versionado (schema_migrations + tx por archivo) al registry
como sqlite_apply_versioned_migrations_go_infra. Migra fn_operations/migrate.go
y registry/migrate.go al consumirla. ~200 LOC duplicadas eliminadas.

- functions/infra/sqlite_apply_versioned_migrations.{go,md,_test.go}: nueva,
  5/5 tests pass. Generaliza fs.FS + dir param (fn_operations usaba embed.FS
  hardcoded). Distinta de sqlite_apply_migrations_go_infra (naive split-by-`;`,
  idempotent-by-error) — esta hace tracking explicito + transactions.
- fn_operations/migrate.go: 111 LOC -> 17. Wrapper sobre infra.ApplyVersionedMigrations.
- registry/migrate.go: idem. Mismo patron copy-paste, ahora unificado.

Smoke: ./fn ops init crea operations.db con schema_migrations poblada.
fn_operations + registry tests: PASS. fn index registra nueva fn (1091 total).

registry/migrate.go

@@ -3,115 +3,16 @@ package registry
 import (
 	"database/sql"
 	"embed"
-	"fmt"
-	"path"
-	"sort"
-	"strconv"
-	"strings"
-	"time"
+
+	"fn-registry/functions/infra"
 )
 
 //go:embed migrations/*.sql
 var migrationsFS embed.FS
 
-const migrationTableSQL = `
-CREATE TABLE IF NOT EXISTS schema_migrations (
-	version    INTEGER PRIMARY KEY,
-	name       TEXT NOT NULL,
-	applied_at TEXT NOT NULL
-);`
-
-// migrate applies pending migrations to the database.
+// migrate applies pending migrations to the registry database via the
+// registry's sqlite_apply_versioned_migrations_go_infra (schema_migrations
+// tracking + per-file transactions).
 func migrate(conn *sql.DB) error {
-	if _, err := conn.Exec(migrationTableSQL); err != nil {
-		return fmt.Errorf("creating schema_migrations table: %w", err)
-	}
-
-	current, err := currentVersion(conn)
-	if err != nil {
-		return err
-	}
-
-	files, err := listMigrations()
-	if err != nil {
-		return err
-	}
-
-	for _, mf := range files {
-		if mf.version <= current {
-			continue
-		}
-
-		content, err := migrationsFS.ReadFile(path.Join("migrations", mf.filename))
-		if err != nil {
-			return fmt.Errorf("reading migration %s: %w", mf.filename, err)
-		}
-
-		tx, err := conn.Begin()
-		if err != nil {
-			return fmt.Errorf("beginning transaction for migration %d: %w", mf.version, err)
-		}
-
-		if _, err := tx.Exec(string(content)); err != nil {
-			tx.Rollback()
-			return fmt.Errorf("applying migration %s: %w", mf.filename, err)
-		}
-
-		if _, err := tx.Exec(
-			"INSERT INTO schema_migrations (version, name, applied_at) VALUES (?, ?, ?)",
-			mf.version, mf.filename, time.Now().UTC().Format(time.RFC3339),
-		); err != nil {
-			tx.Rollback()
-			return fmt.Errorf("recording migration %s: %w", mf.filename, err)
-		}
-
-		if err := tx.Commit(); err != nil {
-			return fmt.Errorf("committing migration %s: %w", mf.filename, err)
-		}
-	}
-
-	return nil
-}
-
-func currentVersion(conn *sql.DB) (int, error) {
-	var v int
-	err := conn.QueryRow("SELECT COALESCE(MAX(version), 0) FROM schema_migrations").Scan(&v)
-	if err != nil {
-		return 0, fmt.Errorf("reading current schema version: %w", err)
-	}
-	return v, nil
-}
-
-type migrationFile struct {
-	version  int
-	filename string
-}
-
-func listMigrations() ([]migrationFile, error) {
-	entries, err := migrationsFS.ReadDir("migrations")
-	if err != nil {
-		return nil, fmt.Errorf("reading migrations directory: %w", err)
-	}
-
-	var files []migrationFile
-	for _, e := range entries {
-		if e.IsDir() || !strings.HasSuffix(e.Name(), ".sql") {
-			continue
-		}
-		parts := strings.SplitN(e.Name(), "_", 2)
-		if len(parts) < 2 {
-			continue
-		}
-		v, err := strconv.Atoi(parts[0])
-		if err != nil {
-			continue
-		}
-		files = append(files, migrationFile{version: v, filename: e.Name()})
-	}
-
-	sort.Slice(files, func(i, j int) bool {
-		return files[i].version < files[j].version
-	})
-
-	return files, nil
+	return infra.ApplyVersionedMigrations(conn, migrationsFS, "migrations")
 }