fix(kiro): align connection status and PostgreSQL dashboards

[warren830]

Summary

• add the standard success and message fields to Kiro's detailed connection-test response so Config UI reports a successful S3 test as Connected
• retain the existing account, stream-count, and diagnostic-hint details in that response
• add regression coverage for the shared Config UI response contract
• remove stale MySQL-style lake. qualifiers from three PostgreSQL Kiro dashboards
• replace remaining MySQL-only date functions and invalid PostgreSQL boolean casts

Root cause

Kiro intentionally returns more connection diagnostics than most plugins, but its ConnectionReport omitted the common success field consumed by Config UI. The request returned HTTP 200 and S3 access succeeded, while the UI interpreted the missing field as false and displayed Disconnected.

Three PostgreSQL dashboards also retained SQL generated from MySQL assumptions: database-qualified lake._tool_kiro_* names, YEAR/MONTH, and a boolean-to-bigint cast. The tables are in PostgreSQL's active schema, so those panels failed when executed against a real PostgreSQL database.

Validation

• go test ./plugins/kiro/... -count=1
• go vet ./plugins/kiro/...
• go build ./plugins/kiro/...
• Config UI TypeScript, ESLint, production build, and 23/23 Vitest tests
• Kiro Playwright suite discovery: 13/13 tests
• real MySQL 8 and PostgreSQL 17 migration/model schema checks across all 44 Go plugins
• real S3 collection on isolated MySQL and PostgreSQL databases: 1,195 objects, zero processing errors, identical resulting row counts
• second collection run on both databases produced no duplicate rows
• MySQL Kiro dashboard SQL: 103/103 queries passed real EXPLAIN
• PostgreSQL Kiro dashboard SQL: 103/103 queries passed real EXPLAIN
• 129/129 dashboard JSON files parsed
• browser verification: Kiro connection test transitions from Testing to Connected

Notes

The detailed connection report remains backward compatible: existing diagnostic fields are unchanged and the shared status fields are additive.