Show build information in web UI

[WilliamK112]

Summary

• pass the existing linker-injected version and commit into the server as explicit build information
• expose build information through the shared UI layout and render it below the repository link in the footer
• add handler and constructor coverage for the build-information data path

Why

The CLI already reports the running version and commit, but the web UI had no access to those values. Operators therefore could not identify the deployed build from the dashboard. This keeps main.Version and main.Commit as the single source of truth while making the same information available on every rendered UI page.

Validation

• go test ./internal/server
• go test ./...
• go test -race ./...
• go vet ./...
• go tool golangci-lint run ./... (0 issues)
• built with -X main.Version=1.2.3 -X main.Commit=abc123; both proxy --version and a live /ui/ response contained proxy 1.2.3 (abc123)
• git diff --check

Closes #256

[Copilot]

Pull request overview

This PR threads linker-injected build metadata (version + commit) from cmd/proxy into the internal server, exposes it via the shared UI Layout, and renders it in the footer so operators can see the deployed build from any UI page.

Changes:

• Add a BuildInfo struct and carry it through server.New(...) into Server and Layout.
• Render build info in the shared footer template.
• Extend server tests to cover the build-info data path and footer rendering.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/server/templates/layout/footer.html	Adds build/version text to the UI footer.
internal/server/server.go	Stores BuildInfo on Server and plumbs it into layout data.
internal/server/server_test.go	Updates test server setup and asserts build info appears in rendered UI and constructor.
internal/server/layout.go	Introduces BuildInfo and includes it in Layout.
cmd/proxy/main.go	Passes linker-injected Version/Commit into server.New(...).

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[andrew]

The shared footer reads .Version and .Commit directly. On pages whose data structs define Version, including VersionShowData and BrowseSourceData, that page field shadows Layout.BuildInfo.Version, so the footer displays package data as the proxy build version. Please reference .BuildInfo.Version and .BuildInfo.Commit explicitly and add coverage for a page with its own Version field.