Upgrade Go to 1.24.3 (#31220)

* Upgrade Go to 1.24.3

Updates the following files:
- server/.go-version: 1.23.9 → 1.24.3
- server/build/Dockerfile.buildenv: golang:1.23.9-bullseye → golang:1.24.3-bullseye
- server/go.mod: go 1.23.0 → go 1.24.3, toolchain go1.23.9 → go1.24.3
- server/public/go.mod: go 1.23.0 → go 1.24.3, toolchain go1.23.9 → go1.24.3

Also fixes non-constant format string errors introduced by Go 1.24.3's stricter format string checking:
- Added response() helper function in slashcommands/util.go for simple string responses
- Removed unused responsef() function from slashcommands/util.go
- Replaced responsef() with response() for translated strings that don't need formatting
- Fixed fmt.Errorf and fmt.Fprintf calls to use proper format verbs instead of string concatenation
- Updated marketplace buildURL to handle format strings conditionally

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* Update generated mocks for Go 1.24.3

Regenerated mocks using mockery v2.53.4 to ensure compatibility with Go 1.24.3.
This addresses mock generation failures that occurred with the Go upgrade.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* Update to bookworm and fix non-existent sha

Signed-off-by: Stavros Foteinopoulos <stafot@gmail.com>

* fix non-constant format string

---------

Signed-off-by: Stavros Foteinopoulos <stafot@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Stavros Foteinopoulos <stafot@gmail.com>

server/build/Dockerfile.buildenv

@@ -1,4 +1,4 @@
-FROM golang:1.23.9-bullseye@sha256:f2ea45502b0565bd554ed2d4954ef1eb434df07ff4cdb867fabb4d2a6b1c0668
+FROM golang:1.24.3-bookworm@sha256:29d97266c1d341b7424e2f5085440b74654ae0b61ecdba206bc12d6264844e21
 
 RUN apt-get update && apt-get install -y make git apt-transport-https ca-certificates curl software-properties-common build-essential zip xmlsec1 jq pgloader