Add a Makefile, so one command is the whole check

Verifying a change meant four invocations — gofmt, go vet, go build, go
test — and remembering the order. `make` is all of them with one exit code.

gofmt needs the wrapper: it reports offending files on stdout and still
exits 0, so a bare `gofmt -l .` in a target would never fail the build.

README.md

@@ -88,14 +88,16 @@ go run .
 Requires Go 1.27+, plus `ffmpeg`, `ffprobe`, and `yt-dlp` on `PATH`. There is nothing to start first:
 the database is a file under `./storage`, created on the first run.
 
-Tests get a fresh database file in a temp directory each, so they need no setup and touch nothing:
+Tests get a fresh database file in a temp directory each, so they need no setup and touch nothing.
+`make` is everything that has to pass before a commit — formatting, `go vet`, and the tests:
 
 ```sh
-go test ./...
+make            # gofmt -l, go vet, go test
+make test       # just the tests
 ```
 
 Templates, stylesheet, and migrations are embedded with `embed.FS`, so a rebuild is needed to see
-template changes. `go build && ./levyraati` is the loop.
+template changes. `make run` is the loop.
 
 ## Admin page