Implement dashboard and audit log templates, add paginated audit log support

- Added `web/templates/{dashboard,audit,base,accounts,account_detail}.html` for a consistent UI.
- Implemented new audit log endpoint (`GET /v1/audit`) with filtering and pagination via `ListAuditEventsPaged`.
- Extended `AuditQueryParams`, added `AuditEventView` for joined actor/target usernames.
- Updated configuration (`goimports` preference), linting rules, and E2E tests.
- No logic changes to existing APIs.

CLAUDE.md

@@ -60,8 +60,8 @@ This is a security-critical project. The following rules are non-negotiable:
 
 ## Go Conventions
 
-- Format all code with `gofmt` before committing
-- Lint with `golangci-lint`; resolve all warnings unless explicitly justified
+- Format all code with `goimports` before committing
+- Lint with `golangci-lint`; resolve all warnings unless explicitly justified. This must be done after every step.
 - Wrap errors with `fmt.Errorf("context: %w", err)` to preserve stack context
 - Prefer explicit error handling over panics; never silently discard errors
 - Use `log/slog` (or goutils equivalents) for structured logging; never `fmt.Println` in production paths