fix(trivy): remove unsupported --no-progress flag from trivy config (#718)

The `trivy config` subcommand does not accept `--no-progress`; the flag
exists only on `trivy image`. Every stack configuration scan therefore
failed with `FATAL Fatal error unknown flag: --no-progress`, and the
"Scan configuration" action on the stack details page has been
non-functional since it shipped.

Removing the flag is the complete fix. `trivy config` is silent by
default, so the flag was redundant even if it had been accepted.

A new Vitest spec pins the exact argument vector
(`['config', '--format', 'json', '--quiet', <stackPath>]`) so a future
edit cannot reintroduce the bug, and exercises the success path end to
end: status transitions to `completed`, misconfig severities tally
correctly, and `highest_severity` rolls up to the worst finding.

backend/src/services/TrivyService.ts

@@ -806,7 +806,7 @@ class TrivyService {
         try {
             const { env, cleanup } = await this.buildEnv();
             try {
-                const args = ['config', '--format', 'json', '--quiet', '--no-progress', resolved];
+                const args = ['config', '--format', 'json', '--quiet', resolved];
                 const { stdout } = await execFileAsync(binary, args, {
                     env,
                     timeout: SCAN_TIMEOUT_MS,