ci: add workflow_dispatch for manual re-runs

Lets you re-run CI from the Forgejo Actions UI without needing a
trivial commit. Useful when:
- An image has been built but the deployed stack didn't pick it up
  (re-run forces a fresh push + any post-CI hooks fire again).
- A transient upstream issue caused a build to fail (HF download
  flake during the voice-bundle step, registry hiccup, etc.) and
  re-running against the same source produces different behaviour.

This commit itself touches .forgejo/workflows/ci.yml so it triggers
a build by the normal paths rule, giving you a fresh :dev image
right now in addition to enabling future manual re-runs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.forgejo/workflows/ci.yml

@@ -42,6 +42,11 @@ on:
       - "assets/**"
       - "fable-mcp/**"
       - ".forgejo/workflows/ci.yml"
+  # Manual trigger from the Forgejo Actions UI. Useful when an image has
+  # been built but the deployment didn't pick it up, or when re-running
+  # against the same source produces different upstream behaviour
+  # (e.g. a transient HF download flake during the voice-bundle step).
+  workflow_dispatch: {}
 
 # Cancel older runs on the same branch when a newer push lands. Tag runs
 # get their own group implicitly (refs/tags/v1.2.3 ≠ refs/heads/dev) and