feat(hooks): name field + beta explainer modal + UI polish

- PG migration 000054 + SQLite v21→v22: add nullable name column
- HookConfig.Name in Go struct, PG/SQLite scan/insert, WS handlers
- Builtin seed writes spec ID as hook name
- UI: name input in create/edit form, displayed in hook list row
- Beta card: "Learn more" button opens modal explaining hooks×skills×MCP
- Default handler_type changed from http to script
- Script editor section: max-h-[50vh] with scroll, border always visible
- i18n: all new keys in en/vi/zh

internal/store/sqlitestore/schema.sql

@@ -1595,6 +1595,7 @@ CREATE TABLE IF NOT EXISTS agent_hooks (
     version      INTEGER NOT NULL DEFAULT 1,
     source       TEXT NOT NULL DEFAULT 'ui' CHECK (source IN ('ui', 'api', 'seed', 'builtin')),
     metadata     TEXT NOT NULL DEFAULT '{}',
+    name         TEXT,
     created_by   TEXT,
     created_at   TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
     updated_at   TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now'))