feat(ui): file browser and connection string builder dialogs (#44)

Enter on File Path inputs opens a file browser (load/save, extension
filter, hidden toggle, overwrite confirm). Enter on Connection String
inputs opens a builder for PostgreSQL, MSSQL and SQLite with masked
password/preview, parsing and optional connection test.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

pkg/ui/load_save_screens.go

@@ -92,6 +92,9 @@ func (se *SchemaEditor) showLoadScreen() {
 		connString = value
 	})
 
+	se.attachFileBrowser(form, "File Path", "load-database", FileBrowserLoad, func() string { return currentFormat })
+	se.attachConnStringBuilder(form, "Connection String", "load-database", func() string { return currentFormat })
+
 	form.AddTextView("Help", getLoadHelpText(), 0, 5, true, false)
 
 	// Buttons
@@ -190,6 +193,8 @@ func (se *SchemaEditor) showSaveScreen() {
 		filePath = value
 	})
 
+	se.attachFileBrowser(form, "File Path", "save-database", FileBrowserSave, func() string { return currentFormat })
+
 	form.AddTextView("Help", getSaveHelpText(), 0, 5, true, false)
 
 	// Buttons
@@ -469,6 +474,8 @@ func getLoadHelpText() string {
 	return `File-based formats: dbml, dctx, drawdb, graphql, json, yaml, gorm, bun, drizzle, prisma, typeorm
 Database formats: pgsql (requires connection string)
 
+Press Enter in File Path to browse files, or in Connection String to open the builder.
+
 Examples:
   - File path: ~/schemas/mydb.dbml or /path/to/schema.json
   - Connection: postgres://user:pass@localhost/dbname`
@@ -520,6 +527,8 @@ func (se *SchemaEditor) showUpdateExistingDatabaseConfirm() {
 func getSaveHelpText() string {
 	return `File-based formats: dbml, dctx, drawdb, graphql, json, yaml, gorm, bun, drizzle, prisma, typeorm, pgsql (SQL export)
 
+Press Enter in File Path to browse for a target.
+
 Examples:
   - File: ~/schemas/mydb.dbml
   - Directory (for code formats): ./models/`
@@ -570,6 +579,9 @@ func (se *SchemaEditor) showImportScreen() {
 		connString = value
 	})
 
+	se.attachFileBrowser(form, "File Path", "import-database", FileBrowserLoad, func() string { return currentFormat })
+	se.attachConnStringBuilder(form, "Connection String", "import-database", func() string { return currentFormat })
+
 	form.AddInputField("Skip Tables (comma-separated)", "", 50, nil, func(value string) {
 		skipTables = value
 	})