ci: sync workflow fixes from main into release-1.10.0
Brings the latest CI/workflow fixes from main into release-1.10.0 so the
nightly build is unblocked and the two branches share the same hardening.
Most important fix: release_nightly.yml's "Verify Nightly Name and Version"
step now uses the anchored grep '^langflow(-nightly)?[[:space:]]' instead of
'grep langflow | grep -v langflow-base | grep -v langflow-sdk'. The old
filter started matching two packages once the langflow-stepflow workspace
package was added, so the name became multi-line and the check failed
(this is what broke the nightly build).
Also carries main's fixes for cross-platform install
(--prerelease=if-necessary-or-explicit), docker build workflows,
db-migration-validation, and the backend test timeout bump (30 -> 40).
3-way merged from the common ancestor, so release-only changes are
preserved; no release-only feature workflows are modified.
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