feat: API key management improvements

- Rename routes: /dashboard/tokens → /dashboard/apikeys, /dashboard/manager/keys → /dashboard/manager/channels
- Add KeyPlain field to store plaintext API keys for re-viewing
- API key list shows masked key (sk-ot-123456****abcd) with eye toggle to reveal
- Copy button with 2s feedback on key list
- TokenNew shows full key + copy after creation
- Increase key prefix display to 12 characters
- Fix SQLite driver: replace gorm.io/driver/sqlite with ncruces/go-sqlite3/gormlite
- Fix user.status === 'active' checks across frontend views
- Add channel store for new channels API
- Update Makefile frontend build to work reliably

BREAKING CHANGE: Existing API keys created before this change will not show their plaintext value (only prefix visible).

backend/internal/store/db.go

@@ -6,9 +6,9 @@ import (
 	"opencatd-open/pkg/config"
 
 	_ "github.com/lib/pq"
+	"github.com/ncruces/go-sqlite3/gormlite"
 	"gorm.io/driver/mysql"
 	"gorm.io/driver/postgres"
-	"gorm.io/driver/sqlite"
 	"gorm.io/gorm"
 )
 
@@ -52,7 +52,7 @@ func sqliteDialector(dsn string) gorm.Dialector {
 	if dsn == "" {
 		dsn = "opencatd.db"
 	}
-	return sqlite.Open(dsn)
+	return gormlite.Open(dsn)
 }
 
 func postgresDialector(dsn string) gorm.Dialector {