fix(docker): move the golang base with the go directive

core/go.mod was bumped to `go 1.26.5` while the goweb stage stayed on
golang:1.23-bookworm. The golang images pin GOTOOLCHAIN=local, so the base can
never fetch a newer toolchain to satisfy the directive:

    go: go.mod requires go >= 1.26.5 (running go 1.23.12; GOTOOLCHAIN=local)

The build dies in 0.086s. A release build that fails in under a second did not
fail to compile — it failed to acquire a toolchain.

This is the fourth instance of the same shape (search-fts5 golang:1.23 vs go
1.26.4, world node:20 vs pnpm@11, search rust:1.89 vs 1.91.1), so I swept the
whole repo: node:20-slim, python:3.12.12-slim-trixie and now golang:1.26 all
satisfy what the tree declares.

Worth noting the frontend is now clean — this build got all the way through
vite to a Go stage, which the asset and identifier fixes are what unblocked.

Co-authored-by: Hanzo Dev <[email protected]>

Dockerfile

@@ -20,7 +20,14 @@ RUN npm run build          # → /fe/build (Vite outDir)
 ################################
 # GOWEB — embed the UI into flowweb
 ################################
-FROM golang:1.23-bookworm AS goweb
+# 1.26 — core/go.mod declares `go 1.26.5`, and the golang images pin
+# GOTOOLCHAIN=local, so the base can never fetch a newer toolchain to satisfy
+# the directive. On 1.23 the build dies instantly with
+#   go: go.mod requires go >= 1.26.5 (running go 1.23.12; GOTOOLCHAIN=local)
+# A release build that fails in under a second did not fail to COMPILE — it
+# failed to acquire a toolchain. Whoever bumps the go directive must move this
+# line in the same commit.
+FROM golang:1.26-bookworm AS goweb
 
 WORKDIR /src
 COPY ./core/ ./core/