feat: remove TimescaleDB, dead PG stores, and storage feature flags

Complete the ClickHouse migration by removing all PostgreSQL analytics
code. PostgreSQL now serves only RBAC, config, and audit — all
observability data is exclusively in ClickHouse.

- Delete 6 dead PostgreSQL store classes (executions, stats, diagrams,
  events, metrics, metrics-query) and 2 integration tests
- Delete RetentionScheduler (ClickHouse TTL handles retention)
- Remove all 7 cameleer.storage.* feature flags from application.yml
- Remove all @ConditionalOnProperty from ClickHouse beans in StorageBeanConfig
- Consolidate 14 Flyway migrations (V1-V14) into single clean V1 with
  only RBAC/config/audit tables (no TimescaleDB, no analytics tables)
- Switch from timescale/timescaledb-ha:pg16 to postgres:16 everywhere
  (docker-compose, deploy/postgres.yaml, test containers)
- Remove TimescaleDB check and /metrics-pipeline from DatabaseAdminController
- Set clickhouse.enabled default to true

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

ui/src/api/queries/admin/database.ts

@@ -9,7 +9,6 @@ export interface DatabaseStatus {
   version: string | null;
   host: string | null;
   schema: string | null;
-  timescaleDb: boolean;
 }
 
 export interface PoolStats {

ui/src/api/schema.d.ts

@@ -2189,10 +2189,8 @@ export interface components {
             version?: string;
             /** @description Database host */
             host?: string;
-            /** @description Current schema search path */
+            /** @description Current schema */
             schema?: string;
-            /** @description Whether TimescaleDB extension is available */
-            timescaleDb?: boolean;
         };
         /** @description Currently running database query */
         ActiveQueryResponse: {