Migrate db and config to mcdsl

- db.Open: delegate to mcdsl/db.Open (WAL, FK, busy timeout, 0600)
- db.Migrate: convert function-based migrations to mcdsl/db.Migration
  SQL strings, delegate to mcdsl/db.Migrate
- db.Snapshot: delegate to mcdsl/db.Snapshot (adds 0600 permissions)
- config: replace local Duration with mcdsl/config.Duration alias,
  replace Load with mcdsl/config.Load[T] + Validator interface
- Remove direct modernc.org/sqlite and go-toml/v2 dependencies
  (now indirect via mcdsl)
- Update TestEnvOverrideInvalidDuration: mcdsl silently ignores
  invalid env duration values (behavioral change from migration)
- All existing tests pass

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

internal/db/db.go

@@ -3,9 +3,8 @@ package db
 import (
 	"database/sql"
 	"fmt"
-	"os"
 
-	_ "modernc.org/sqlite"
+	mcdsldb "git.wntrmute.dev/kyle/mcdsl/db"
 )
 
 // Store wraps a SQLite database connection for mc-proxy persistence.
@@ -14,36 +13,14 @@ type Store struct {
 }
 
 // Open opens (or creates) the SQLite database at path with WAL mode,
-// foreign keys, and a busy timeout. The file is created with 0600 permissions.
+// foreign keys, and a busy timeout. The file is created with 0600
+// permissions.
 func Open(path string) (*Store, error) {
-	// Ensure the file has restrictive permissions if it doesn't exist.
-	if _, err := os.Stat(path); os.IsNotExist(err) {
-		f, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0600)
-		if err != nil {
-			return nil, fmt.Errorf("creating database file: %w", err)
-		}
-		f.Close()
-	}
-
-	db, err := sql.Open("sqlite", path)
+	database, err := mcdsldb.Open(path)
 	if err != nil {
 		return nil, fmt.Errorf("opening database: %w", err)
 	}
-
-	// Apply connection pragmas.
-	pragmas := []string{
-		"PRAGMA journal_mode = WAL",
-		"PRAGMA foreign_keys = ON",
-		"PRAGMA busy_timeout = 5000",
-	}
-	for _, p := range pragmas {
-		if _, err := db.Exec(p); err != nil {
-			db.Close()
-			return nil, fmt.Errorf("setting pragma %q: %w", p, err)
-		}
-	}
-
-	return &Store{db: db}, nil
+	return &Store{db: database}, nil
 }
 
 // Close closes the database connection.
@@ -51,6 +28,11 @@ func (s *Store) Close() error {
 	return s.db.Close()
 }
 
+// DB returns the underlying *sql.DB for use with mcdsl functions.
+func (s *Store) DB() *sql.DB {
+	return s.db
+}
+
 // IsEmpty returns true if the listeners table has no rows.
 // Used to determine if the database needs seeding from config.
 func (s *Store) IsEmpty() (bool, error) {