✨ Add buf + goose, fix PATH order, rewrite README ✨

Add buf (modern protobuf toolchain) and goose (Go-native DB migration
runner) to complete the Go dev toolchain. Fix PATH order so baked image
tools in /usr/local/bin always take precedence over anything installed
at runtime into $GOPATH/bin. Full README rewrite following canonical
section order.
- Dockerfile: insert /usr/local/bin between /usr/local/go/bin and
/usr/local/share/go/bin in both build and final stage ENV PATH
- rootfs/etc/profile.d/go.sh: same PATH fix; explicit /usr/local/bin
guard added; $GOPATH/bin appended last
- rootfs/root/docker/setup/05-custom.sh: add buf@latest and
goose/v3@latest installs with descriptive comments
- README.md: full rewrite — H1 title, canonical section order (Pull,
Docker, Tools table, Env vars, PATH order, Persistence, Cross-compile,
Development, License); accurate tool list matching actual image content

Dockerfile
README.md
rootfs/etc/profile.d/go.sh
rootfs/root/docker/setup/05-custom.sh

Dockerfile

@@ -20,7 +20,7 @@ ARG PHP_VERSION="system"
 ARG NODE_VERSION="system"
 ARG NODE_MANAGER="system"
 
-ARG IMAGE_REPO="casjaysdevdocker/go"
+ARG IMAGE_REPO="casjaysdev/go"
 ARG IMAGE_VERSION="latest"
 ARG CONTAINER_VERSION=""
 
@@ -58,7 +58,7 @@ ARG PACK_LIST="git make bash tini ca-certificates openssh-client curl wget tar t
 
 ENV ENV=~/.profile
 ENV SHELL="/bin/sh"
-ENV PATH="/usr/local/go/bin:/usr/local/share/go/bin:${PATH}"
+ENV PATH="/usr/local/go/bin:/usr/local/bin:/usr/local/share/go/bin:${PATH}"
 ENV TZ="${TIMEZONE}"
 ENV TIMEZONE="${TZ}"
 ENV LANG="${LANGUAGE}"
@@ -234,7 +234,7 @@ LABEL com.github.containers.toolbox="false"
 
 ENV ENV=~/.bashrc
 ENV USER="${USER}"
-ENV PATH="/usr/local/go/bin:/usr/local/share/go/bin:${PATH}"
+ENV PATH="/usr/local/go/bin:/usr/local/bin:/usr/local/share/go/bin:${PATH}"
 ENV TZ="${TIMEZONE}"
 ENV SHELL="/bin/bash"
 ENV TIMEZONE="${TZ}"