docs: present Grocery Run as an archived project

[itsreverence]

Summary

• replace the IDE/setup-first README with an honest archived-project portfolio case study
• document Grocery Run’s product areas, layered Spring architecture, route generation, testing scope, attribution, and historical limitations
• add a privacy-safe landing-page screenshot captured from a fresh local run
• add the repository-wide MIT license authorized by the copyright contributors and align Maven metadata
• replace the fixed local database credential with an ignored .env workflow and obvious example placeholder
• pin PostgreSQL 17.9 to an exact multi-platform image digest, bind it to loopback, use the standard data path, and add TCP readiness checks
• remove repository-local agent skill artifacts that do not belong in the product archive
• remove Dependabot configuration from the frozen archive

This intentionally does not modernize the historical application, dependency graph, or test architecture.

Verification

• docker compose --env-file .env.example config rendered successfully
• exact PostgreSQL 17.9 image digest started from a fresh named volume, reached healthy state through its TCP healthcheck, and accepted TCP connections
• containerized JDK 21 service tests passed: 21 tests, 0 failures, 0 errors
• independent full-suite run with isolated PostgreSQL passed: 22 tests, 0 failures, 0 errors
• containerized ./mvnw -DskipTests package completed with BUILD SUCCESS
• the full Spring application started against fresh PostgreSQL
• the landing page returned successfully on port 8080
• the new 1440×1100 screenshot was inspected for layout defects and private information
• README local links resolve and all contributor/MIT links returned HTTP 200
• current-tree checks found no stale Railway URL, old local password, floating PostgreSQL tag, agent-skill markers, or Dependabot references
• reachable-history heuristic scan found no private keys, GitHub tokens, or high-confidence generic secret assignments
• runtime containers, network, Maven cache, and database volume were removed after testing
• git diff --check

Archive follow-up

After review, merge this change, close the refreshed Dependabot pull requests, clear the dead Railway homepage, set focused metadata, disable Issues/Projects/Wiki, and rearchive the repository.

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