The standings should be reproducible from the match results alone. Build the ranking so points, goal difference and the final tie rule are applied consistently.
Build the implementation in SQL under /app, with /app/run.sh as its entry point. Read one JSON request from standard input and write one JSON result to standard output. Input has unique team strings and matches with home, away, home_score and away_score. Scores must be nonnegative integers and opponents distinct known teams. Award 3 points for a win and 1 each for a draw. Return records team, points, difference sorted by descending points, descending goal difference, then team name. Include teams with no matches. Reject invalid matches or duplicate teams.
Reject inputs that violate an explicit validation rule with exit status 2, no standard output, and {"error":"invalid_input"} on standard error. For valid input, exit with status 0. Keep the implementation reusable for new inputs; it must work offline and must not depend on the example data being the only data it receives.
Repair or replace the unfinished /app/run.sh and add source files under /app. Malformed JSON must use the same invalid-input response. Do not read /tests or /oracle from the application.