feat: implement multitenancy with tenant isolation + environment support

Adds configurable tenant ID (CAMELEER_TENANT_ID env var, default:
"default") and environment as a first-class concept. Each server
instance serves one tenant with multiple environments.

Changes across 36 files:
- TenantProperties config bean for tenant ID injection
- AgentInfo: added environmentId field
- AgentRegistrationRequest: added environmentId field
- All 9 ClickHouse stores: inject tenant ID, replace hardcoded
  "default" constant, add environment to writes/reads
- ChunkAccumulator: configurable tenant ID + environment resolver
- MergedExecution/ProcessorBatch/BufferedLogEntry: added environment
- ClickHouse init.sql: added environment column to all tables,
  updated ORDER BY (tenant→time→env→app), added tenant_id to
  usage_events, updated all MV GROUP BY clauses
- Controllers: pass environmentId through registration/auto-heal
- K8s deploy: added CAMELEER_TENANT_ID env var
- All tests updated for new signatures

Closes #123

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/dto/AgentRegistrationRequest.java

@@ -11,6 +11,7 @@ public record AgentRegistrationRequest(
         @NotNull String instanceId,
         @NotNull String displayName,
         @Schema(defaultValue = "default") String applicationId,
+        @Schema(defaultValue = "default") String environmentId,
         String version,
         List<String> routeIds,
         Map<String, Object> capabilities