fix(redisproxy): support classic ArgoCD applications without agent prefix

## Problem
The redisproxy implementation strictly required all Redis keys to start with
an agent name prefix in the format 'agentName_'. This worked for agent-managed
applications but broke for classic ArgoCD applications (using token authentication)
which generate Redis keys without any prefix.

When a key without the prefix arrived at redisproxy, the extractAgentNameFromRedisCommandKey
function would fail with 'unexpected lack of "_" namespace/name separator' error,
causing PUB/SUB connections to drop and resource requests for classic applications
to fail completely.

## Solution
Modified extractAgentNameFromRedisCommandKey function to gracefully handle Redis keys
without the agent prefix by:

1. Detecting keys without underscore separator in the namespace field
2. Returning empty string (instead of error) for non-agent-prefixed keys
3. This allows these keys to be routed to the principal Redis instead of failing

The routing logic in handleConnectionMessageLoop already supports this via the
'if agentName != ""' check, which will forward local keys to principal Redis.

## Changes Made

### principal/redisproxy/redisproxy.go
- Modified extractAgentNameFromRedisCommandKey() function
- Changed error case for missing underscore to return empty string with debug log
- Updated comments to clarify behavior for classic vs agent-managed applications

### principal/redisproxy/redisproxy_test.go
- Updated test cases to reflect new behavior
- Changed 'errorExpected: true' to 'errorExpected: false' for classic app keys
- Updated test descriptions to clarify that keys without prefix are classic apps

## Testing
✅ All existing tests pass (21 tests in redisproxy package)
✅ Code compiles without errors
✅ Multi-platform Docker image builds successfully (linux/amd64 and linux/arm64)

## Impact
- ✅ Agent-managed applications continue to work as before
- ✅ Classic ArgoCD applications now work correctly
- ✅ Mixed environments with both types of applications are now supported
- ✅ No breaking changes to existing functionality

## Example Routing
- Agent-managed key: 'app|managed-resources|agent-managed_my-app|1.8.3'
  → Routed to agent via gRPC
- Classic app key: 'app|managed-resources|my-app|1.8.3'
  → Routed to principal Redis (control plane)

Author: petrlebedev

.gitignore

@@ -6,3 +6,4 @@ vendor/
 build/
 __pycache__
 site/
+local*.sh

principal/redisproxy/redisproxy.go

@@ -814,10 +814,11 @@ func extractAgentNameFromRedisCommandKey(redisKey string, logCtx *logrus.Entry)
 	namespaceAndName := splitByPipe[2]
 
 	// It is not possible to create a namespace name containing a '_' value, so this is a correct delimiter
+	// If the namespace/name doesn't contain '_', it's a classic (non-agent-managed) application
+	// and should be forwarded to principal redis
 	if !strings.Contains(namespaceAndName, "_") {
-		errMsg := fmt.Sprintf("unexpected lack of '_' namespace/name separate: '%s'", redisKey)
-		logCtx.Error(errMsg)
-		return "", fmt.Errorf("%s", errMsg)
+		logCtx.Debugf("Redis key without agent prefix detected: '%s'. Routing to principal redis.", redisKey)
+		return "", nil
 	}
 
 	// namespace is the agent name

principal/redisproxy/redisproxy_test.go

@@ -51,16 +51,16 @@ func Test_extractAgentNameFromRedisCommandKey(t *testing.T) {
 			errorExpected: false,
 		},
 		{
-			name:          "'app|managed-resources' with only namespace",
+			name:          "'app|managed-resources' with only namespace (classic app without agent prefix)",
 			key:           "app|managed-resources|my-app|1.8.3",
 			value:         "",
-			errorExpected: true,
+			errorExpected: false,
 		},
 		{
-			name:          "'app|resources-tree' with only namespace",
+			name:          "'app|resources-tree' with only namespace (classic app without agent prefix)",
 			key:           "app|resources-tree|my-app|1.8.3.gz",
 			value:         "",
-			errorExpected: true,
+			errorExpected: false,
 		},
 		{
 			name:          "'app|resources-tree' with unexpected field format",