fix: update Dockerfile to use Go 1.25.7

Updated Dockerfile to use golang:1.25.7-alpine base image
to match go.mod requirements.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: ndbroadbent

Dockerfile

@@ -15,7 +15,7 @@ RUN bun install --frozen-lockfile
 COPY web/ ./
 RUN bun run build
 
-FROM golang:1.25.5-alpine AS builder
+FROM golang:1.25.7-alpine AS builder
 
 RUN apk add --no-cache git ca-certificates make gcc musl-dev nodejs npm