Add justfile and essential recipes. Add unit tests. Add linter and fix linter errors.

justfile

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+set shell := ["bash", "-eu", "-o", "pipefail", "-c"]
+
+root_dir := justfile_directory()
+api_project := root_dir + "/api/App/App.csproj"
+api_solution := root_dir + "/api/Api.slnx"
+ui_dir := root_dir + "/ui"
+db_dir := root_dir + "/api/Database"
+db_file := db_dir + "/klapi.db"
+db_init_sql := db_dir + "/init.sql"
+
+default:
+	@just --list
+
+dev:
+	./start.sh
+
+api-restore:
+	dotnet restore {{api_project}}
+
+api-build:
+	dotnet build {{api_project}}
+
+api-clean:
+	dotnet clean {{api_project}}
+
+api-run:
+	dotnet run --project {{api_project}}
+
+api-watch:
+	dotnet watch --project {{api_project}} run
+
+api-test:
+	dotnet test {{api_solution}}
+
+api-publish:
+	dotnet publish {{api_project}} -c Release
+
+ui-install:
+	cd {{ui_dir}} && bun install
+
+ui-dev:
+	cd {{ui_dir}} && bun dev
+
+ui-build:
+	cd {{ui_dir}} && bun run build
+
+ui-test:
+	cd {{ui_dir}} && bun run test
+
+ui-lint:
+	cd {{ui_dir}} && bun run lint
+
+db-setup:
+	mkdir -p {{db_dir}}
+	if ! command -v sqlite3 >/dev/null 2>&1; then echo "sqlite3 is required for db-setup" >&2; exit 1; fi
+	sqlite3 {{db_file}} < {{db_init_sql}}
+
+db-reset:
+	rm -f {{db_file}}
+	just db-setup
+
+db-shell:
+	if ! command -v sqlite3 >/dev/null 2>&1; then echo "sqlite3 is required for db-shell" >&2; exit 1; fi
+	sqlite3 {{db_file}}