agent: add separate glibc build with NVML support (#1618)

purego requires dynamic linking, so split the agent builds:
- Default: static binary without NVML (works on musl/alpine)
- Glibc: dynamic binary with NVML support via purego

Changes:
- Add glibc build tag to conditionally include NVML code
- Add beszel-agent-linux-amd64-glibc build/archive in goreleaser
- Update ghupdate to use glibc binary on glibc systems
- Switch nvidia dockerfile to golang:bookworm with -tags glibc

internal/dockerfile_agent_nvidia

@@ -1,4 +1,4 @@
-FROM --platform=$BUILDPLATFORM golang:alpine AS builder
+FROM --platform=$BUILDPLATFORM golang:bookworm AS builder
 
 WORKDIR /app
 
@@ -10,7 +10,7 @@ COPY . ./
 
 # Build
 ARG TARGETOS TARGETARCH
-RUN CGO_ENABLED=0 GOGC=75 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -ldflags "-w -s" -o /agent ./internal/cmd/agent
+RUN CGO_ENABLED=0 GOGC=75 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -tags glibc -ldflags "-w -s" -o /agent ./internal/cmd/agent
 
 # --------------------------
 # Smartmontools builder stage