Create FIPS complaint boards plugin

[stafot]

🔒 Add FIPS 140-2 Compliance Support for Mattermost Boards Plugin

Summary

This PR implements FIPS (Federal Information Processing Standards) 140-2 compliance for the Mattermost Boards plugin, enabling secure deployment in government and enterprise environments that require cryptographic validation.
Changes Made

🛠️ FIPS Build Infrastructure

Added FIPS build targets: server-fips, bundle-fips, dist-fips, dist-all
FIPS Docker integration: Uses cgr.dev/mattermost.com/go-msft-fips:1.24.6 for FIPS-validated Go compilation
Dual distribution support: Builds both regular and FIPS-compliant plugin bundles

🔧 Plugin Compatibility Fixes

Binary naming standardization: FIPS bundles now contain correctly named binaries (plugin-linux-amd64) for server compatibility
Fixed broken variable references: Resolved FOCALBOARD_PLUGIN_PATH → BOARD_PLUGIN_PATH inconsistencies
Updated Go version: Upgraded to Go 1.24.6 for latest security patches

Testing

✅ FIPS server compatibility: Tested with FIPS-enabled Mattermost server
✅ Plugin loading: Verified successful installation and startup
✅ Functionality: Confirmed full plugin operation in FIPS mode
✅ Security compliance: Maintains FIPS 140-2 cryptographic standards

Breaking Changes
None - fully backward compatible with existing installations.

Deployment

FIPS-compliant organizations can now deploy the Boards plugin using the -fips bundle variant while maintaining full functionality and security compliance.
Related: Part of broader FIPS compliance initiative across Mattermost plugin ecosystem.

Ticket Link

https://mattermost.atlassian.net/browse/CLD-9417

[esarafianou]

Thanks Stavro, a few comments:

[harshilsharma63]

Only change required is not returning that error there as in comment

[harshilsharma63]

Deferring the Makefile changes related to FIPS to @esarafianou , but boards changes look good.

[esarafianou]

@stafot great work, I didn't know we were not building the Boards plugin during CI at all.

Just one comment for naming. It should stay Boards to distinguish itself from the community supported focalboard.

[agarciamontoro]

Rebased this branch on top of the v9.1.6 tag to build off the latest prepackaged version. Sorry for the force-push!

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity.
A core team member will check in on the status of the PR to help with questions.
Thank you for your contribution!

[agarciamontoro]

Merged up to the v9.1.7 tag for prepackaging for MM v11.1

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity.
A core team member will check in on the status of the PR to help with questions.
Thank you for your contribution!

[agarciamontoro]

Merged up to the v9.2.1 tag for prepackaging for MM v11.2

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity.
A core team member will check in on the status of the PR to help with questions.
Thank you for your contribution!

[agarciamontoro]

Merged up to the v9.2.2 tag for prepackaging for MM v11.4