chore: remove generated openapi.json from tracking, add test and docs

- Remove resources/gen/openapi.json from git (served dynamically at /api/openapi.json)
- Add resources/gen/ to .gitignore
- Add OpenAPI spec validation test (paths, schemas, serialization)
- Restore removed doc-comment on get_version
- Fix cargo fmt violation in mod.rs import
- Update CLAUDE.md: test count (~208), generate-openapi command, justfile reference

CLAUDE.md

@@ -8,15 +8,19 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 cargo build                          # Dev build
 cargo build --release                # Optimized release build
 cargo run                            # Run server (port 8086)
-cargo test --workspace               # Run all tests (~112)
+cargo test --workspace               # Run all tests (~208)
 cargo test <test_name>               # Run a single test by name
 cargo test --features test_utils     # Run tests that use mockall mocks
 cargo clippy -- -D warnings          # Lint (zero warnings policy)
 cargo fmt --all --check              # Format check
 cargo fmt --all                      # Auto-format
 RUST_LOG=debug cargo run             # Run with debug logging
+cargo run --bin generate-openapi     # Regenerate resources/gen/openapi.json
 ```
 
+A `justfile` is available for common tasks (`just --list` to see all). Key recipes: `just check` (fmt + clippy), `just test`, `just openapi`.
+
+
 Requires **Rust 1.93+** (edition 2024) and **PostgreSQL 13+** (with `pg_trgm` and `ltree` extensions).
 
 Database setup: `docker compose up -d postgres` — schema is applied automatically via sqlx migrations on app startup. Migration files live in `migrations/`. For local dev, set `DATABASE_URL` in `.env` (see `example.env`).