fix(docker): bump build image to golang:1.26 to match go.mod 1.26.1

go.mod requires >=1.26.1 but the Dockerfile pinned golang:1.25 -> 'go.mod
requires go >= 1.26.1 (running go 1.25.11)'. Also revert the ci.yml XDG hack:
the real rootless-buildah fix is a user ~/.config/containers/storage.conf (vfs +
writable runroot), which fixes plain buildah for every repo without workflow
changes.

.gitea/workflows/ci.yml

@@ -63,11 +63,6 @@ jobs:
 
       - name: Build and push to local registry
         run: |
-          # The act_runner is a systemd service with no login session, so
-          # XDG_RUNTIME_DIR is unset and rootless buildah falls back to the
-          # root-owned /run/containers ("mkdir /run/containers: permission
-          # denied"). Point its runroot at a writable per-job temp dir instead.
-          export XDG_RUNTIME_DIR="$(mktemp -d /tmp/buildah-run.XXXXXX)"
           REGISTRY="localhost:5000"
           REF="${REGISTRY}/${{ env.IMAGE }}:${{ steps.meta.outputs.sha-tag }}"
           buildah build \

Dockerfile

@@ -3,7 +3,7 @@
 # ── build ───────────────────────────────────────────────────────────────────
 # templ output (*_templ.go) and the vendored htmx asset are committed, so a
 # plain `go build` produces a self-contained binary — no codegen, no CDN.
-FROM golang:1.25 AS build
+FROM golang:1.26 AS build
 
 WORKDIR /src