Fail interrupted groundings at boot and bound hand grounding

At boot, after the job runner fails the jobs a previous process left
running, FailInterruptedGroundings sets every dinner still pending with
no ground_dinner job queued or running to failed (interrupted). A crash
mid-job, or between saving a dinner and enqueuing its job, no longer
leaves the dinner pending forever.

A search failure on recipe-candidates or ground now logs only the reason
code search_failed, never the wrapped error, which may quote the
provider; the response stays redacted.

When the grounding job cannot be enqueued, POST /dinners answers 201
with the saved dinner failed (grounding_error) and grounding_job_id
null, instead of a 500 that hid the dinner it had created.

Grounding a candidate or link by hand runs under a 90-second deadline
(fetch, photo, normalize_recipe); past it the request answers 504
ground_timeout and the dinner is unchanged.

Maestro task: 0cbaa5bf-8be4-4cbd-aab2-891e7f1bc2b5

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/dinners/export_test.go

@@ -0,0 +1,14 @@
+package dinners
+
+import (
+	"testing"
+	"time"
+)
+
+// SetGroundTimeout sets the deadline of grounding by hand until t ends. A
+// test calling it must not run in parallel.
+func SetGroundTimeout(t *testing.T, d time.Duration) {
+	old := groundTimeout
+	groundTimeout = d
+	t.Cleanup(func() { groundTimeout = old })
+}