Move the package into src/

Thirty-seven entries in the root, most of them .go files. The assets had to
come along: //go:embed cannot reach outside its own directory, so
templates/, static/ and migrations/ live beside the code that embeds them,
and testdata/ beside the test that reads it. storage/ stays put — runtime
data, not source.

go build now needs -o. Without it the output would be named after the
package directory and collide with src/ itself.

Dockerfile

@@ -5,7 +5,7 @@ WORKDIR /src
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .
-RUN CGO_ENABLED=0 go build -ldflags "-X main.version=${VERSION}" -o /levyraati .
+RUN CGO_ENABLED=0 go build -ldflags "-X main.version=${VERSION}" -o /levyraati ./src
 
 FROM alpine:3.24
 # yt-dlp rots against YouTube. Alpine's active branch tracks it closely (3.24 carries the current