FindProductSummary and FindColorDetail aggregate pan.position via GROUP_CONCAT
with a LEFT JOIN. When a product has no pans the join produces all-NULL rows,
causing GROUP_CONCAT to return NULL, which cannot be scanned into a Go string —
making the entire summary query fail silently and the frontend show an empty table.
Fix: wrap both GROUP_CONCAT(pan.position) calls with COALESCE(..., '').
Also removes CostPrice from the generated InvProduct model (field dropped from schema).
Adds integration tests TestFindProductSummaryNoPans and TestFindColorDetailNoPans
to guard against this class of NULL-scan regression.
Align origin/main with upstream/main (GitHub). The two branches
diverged due to pre-rebase vs post-rebase merge commits for the
k8s-amd64-dockerfiles feature.
Includes: multi-stage Go compilation Dockerfiles, pan-bolt
inventory features, CRM relations, Excel import tooling,
proto/gRPC updates, migration scripts, and tools/ directory.
Excludes deploy/bin/ pre-compiled binaries (arm64, not needed
for amd64 K3s cluster; builds use multi-stage Dockerfiles now).
