feat: sanitize container log output beyond Content-Type

Add SanitizeLogs() that strips ANSI escape sequences and non-printable
control characters (preserving newlines, carriage returns, and tabs)
from all container and deployment log output paths:

- HandleAppLogs (text/plain response)
- HandleDeploymentLogsAPI (JSON response)
- HandleContainerLogsAPI (JSON response)

Container log output is attacker-controlled data. Content-Type alone
is insufficient — the data itself must be sanitized before serving.

Includes comprehensive test coverage for the sanitization function.

internal/handlers/app.go

@@ -499,7 +499,7 @@ func (h *Handlers) HandleAppLogs() http.HandlerFunc {
 			return
 		}
 
-		_, _ = writer.Write([]byte(logs)) // #nosec G705 -- Content-Type is text/plain, no XSS risk
+		_, _ = writer.Write([]byte(SanitizeLogs(logs))) // #nosec G705 -- logs sanitized, Content-Type is text/plain
 	}
 }
 
@@ -534,7 +534,7 @@ func (h *Handlers) HandleDeploymentLogsAPI() http.HandlerFunc {
 
 		logs := ""
 		if deployment.Logs.Valid {
-			logs = deployment.Logs.String
+			logs = SanitizeLogs(deployment.Logs.String)
 		}
 
 		response := map[string]any{
@@ -661,7 +661,7 @@ func (h *Handlers) HandleContainerLogsAPI() http.HandlerFunc {
 		}
 
 		response := map[string]any{
-			"logs":   logs,
+			"logs":   SanitizeLogs(logs),
 			"status": status,
 		}