Fix: Redis AUTH must come before SELECT

The SELECT command was failing because Redis requires authentication first.
Reordered commands: connect -> auth -> select.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

openresty/lua/redis_helper.lua

@@ -18,23 +18,21 @@ local function get_redis_connection()
         return nil
     end
 
-    -- Select the correct Redis database (db 1, matching backend config)
-    local db = tonumber(os.getenv("REDIS_DB")) or 1
-    local res, err = red:select(db)
-    if not res then
-        ngx.log(ngx.ERR, "Failed to select Redis database: ", err)
-        return nil
-    end
-
-    -- Authenticate if password is set
+    -- Authenticate FIRST if password is set (must happen before any other commands)
     if REDIS_PASSWORD and REDIS_PASSWORD ~= "" then
         local res, err = red:auth(REDIS_PASSWORD)
         if not res then
             ngx.log(ngx.ERR, "Failed to authenticate to Redis: ", err)
             return nil
         end
-    else
-        ngx.log(ngx.WARN, "No Redis password set, trying without auth")
+    end
+
+    -- Select the correct Redis database (db 1, matching backend config)
+    local db = tonumber(os.getenv("REDIS_DB")) or 1
+    local res, err = red:select(db)
+    if not res then
+        ngx.log(ngx.ERR, "Failed to select Redis database: ", err)
+        return nil
     end
 
     return red