feat(cli,ci): admin reset-password + migrate subcommands; test-DB isolation + CI integration job

#321 — `minstrel admin reset-password [-user admin] [-password X]`:
loads config, updates BOTH password_hash (bcrypt) and subsonic_password
(plaintext, for Subsonic t+s) so neither auth path is left stale;
generates+prints a strong password when -password is omitted. Recovers
a locked-out operator without DB surgery. Subcommand dispatch added to
main.go (os.Args switch before flag-parse; server path untouched) plus
a `minstrel migrate` subcommand exposing db.Migrate standalone.

#339 — integration tests no longer truncate the dev DB:
- deploy/initdb creates minstrel_test on a fresh compose volume;
  `make test-integration` ensures it idempotently and points
  MINSTREL_TEST_DATABASE_URL at minstrel_test.
- docker-compose.yml + README updated.

CI integration job (test-go.yml): the prior workflow only ran
`go test -short -race` with no DB, so the entire integration suite
silently t.Skip'd — "CI green" never covered API/db/scanner. New
`integration` job runs the full `go test -race` against an ephemeral
Postgres service, using the act_runner shared-daemon pattern: no
published ports, discover the service container by job-name filter via
the docker socket, reach it by bridge IP, hard exactly-one assertion +
dev-compose-name reject (a wrong target would truncate real data),
TCP-wait, `minstrel migrate`, then test. Fast `test` job kept as the
quick gate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Makefile

@@ -1,4 +1,4 @@
-.PHONY: generate test test-short lint build
+.PHONY: generate test test-short test-integration lint build
 
 SQLC_VERSION := 1.31.1
 
@@ -11,6 +11,14 @@ test:
 test-short:
 	go test -short -race ./...
 
+# Full suite incl. integration tests, against the dedicated minstrel_test
+# DB so a run never truncates the dev `minstrel` DB (Fable #339). Ensures
+# the test DB exists (idempotent — createdb errors if present, ignored).
+test-integration:
+	docker compose up -d postgres
+	-docker compose exec -T postgres createdb -U minstrel minstrel_test
+	MINSTREL_TEST_DATABASE_URL=postgres://minstrel:minstrel@localhost:5432/minstrel_test?sslmode=disable go test -race ./...
+
 lint:
 	golangci-lint run ./...