fix: remove manual event from build-ci-image to fix issue automation

build-ci-image.yml had event:[push,manual] which caused it to run
on every manual pipeline trigger. Its registry_user/registry_password
secrets don't have the manual event, causing all manual pipelines to
error. Removed manual from its event list since it only needs push.

Reverted evaluate conditions (Woodpecker evaluates secrets before
conditions, so evaluate can't prevent missing-secret errors).

[ci skip]

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.woodpecker/build-ci-image.yml

@@ -1,12 +1,11 @@
 # Build the CI tools Docker image used by all infra pipelines.
-# Triggers on changes to ci/Dockerfile or manual dispatch.
+# Triggers on changes to ci/Dockerfile only (push to master).
 
 when:
-  - event: [push, manual]
-    branch: master
-    evaluate: 'CI_PIPELINE_VARIABLE_ISSUE_NUMBER == ""'
-    path:
-      include:
+  event: push
+  branch: master
+  path:
+    include:
       - 'ci/Dockerfile'
 
 steps: