fix!: require environment on diagram lookup and attribute keys queries

Closes two cross-env data leakage paths. Both endpoints previously
returned data aggregated across all environments, so a diagram or
attribute key from dev could appear in a prod UI query (and vice versa).

B1: GET /api/v1/diagrams?application=&routeId= now requires
?environment= and resolves agents via
registryService.findByApplicationAndEnvironment instead of
findByApplication. Prevents serving a dev diagram for a prod route.

B2: GET /api/v1/search/attributes/keys now requires ?environment=.
SearchIndex.distinctAttributeKeys gains an environment parameter and
the ClickHouse query adds the env filter alongside the existing
tenant_id filter. Prevents prod attribute names leaking into dev
autocompletion (and vice versa).

SPA hooks updated to thread environment through from
useEnvironmentStore; query keys include environment so React Query
re-fetches on env switch. No call-site changes needed — hook
signatures unchanged.

B3 (AgentMetricsController env scope) deferred to P3C: agent-env is
effectively 1:1 today via the instance_id naming
({envSlug}-{appSlug}-{replicaIndex}), and the URL migration in P3C
to /api/v1/environments/{env}/agents/{agentId}/metrics naturally
introduces env from path. A minimal P1 fix would regress the "view
metrics of a killed agent" case.

BREAKING CHANGE: Both endpoints now require ?environment= (slug).
Clients omitting the parameter receive 400.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-core/src/main/java/com/cameleer/server/core/search/SearchService.java

@@ -25,8 +25,8 @@ public class SearchService {
         return searchIndex.count(request);
     }
 
-    public List<String> distinctAttributeKeys() {
-        return searchIndex.distinctAttributeKeys();
+    public List<String> distinctAttributeKeys(String environment) {
+        return searchIndex.distinctAttributeKeys(environment);
     }
 
     public ExecutionStats stats(Instant from, Instant to) {

cameleer-server-core/src/main/java/com/cameleer/server/core/storage/SearchIndex.java

@@ -17,6 +17,6 @@ public interface SearchIndex {
 
     void delete(String executionId);
 
-    /** Returns distinct attribute key names across all executions. */
-    List<String> distinctAttributeKeys();
+    /** Returns distinct attribute key names across executions in the given environment. */
+    List<String> distinctAttributeKeys(String environment);
 }