Add HTMX-based UI templates and handlers for account and audit management

- Introduced `web/templates/` for HTMX-fragmented pages (`dashboard`, `accounts`, `account_detail`, `error_fragment`, etc.).
- Implemented UI routes for account CRUD, audit log display, and login/logout with CSRF protection.
- Added `internal/ui/` package for handlers, CSRF manager, session validation, and token issuance.
- Updated documentation to include new UI features and templates directory structure.
- Security: Double-submit CSRF cookies, constant-time HMAC validation, login password/Argon2id re-verification at all steps to prevent bypass.

PROJECT.md

@@ -55,10 +55,14 @@ Performance is secondary, and can be tuned later.
   critical for this.
   + We will also need to build client libraries in several languages
     later on.
-+ There should be two command line tools associated with MCIAS:
++ There are four command line tools associated with MCIAS:
   + mciassrv is the authentication server.
   + mciasctl is the tool for admins to create and manage accounts, issue
     or revoke tokens, and manage postgres database credentials.
+  + mciasdb is the offline database maintenance tool for break-glass
+    recovery, bootstrap, and direct SQLite operations.
+  + mciasgrpcctl is the gRPC admin CLI companion (mirrors mciasctl
+    over gRPC).
 
 ## Notes