docs: add applies_to frontmatter and section-level tagging

- Add applies_to (stack: ga, serverless: ga) and products to index.md and setup.md
- Add section-level applies_to for Step 2 (Configure Filebeat): stack only, serverless unavailable
- Add frontmatter to Monolog_v3.md and fix typo (contex -> context)

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: alexandra5000

docs/Monolog_v3.md

@@ -1,3 +1,9 @@
+---
+applies_to:
+  stack: ga
+  serverless: ga
+---
+
 # Monolog v3.x
 
 ## Initialize the Formatter

docs/reference/index.md

@@ -1,4 +1,7 @@
 ---
+applies_to:
+  stack: ga
+  serverless: ga
 mapped_pages:
   - https://www.elastic.co/guide/en/ecs-logging/php/current/intro.html
   - https://www.elastic.co/guide/en/ecs-logging/php/current/index.html

docs/reference/setup.md

@@ -1,4 +1,7 @@
 ---
+applies_to:
+  stack: ga
+  serverless: ga
 mapped_pages:
   - https://www.elastic.co/guide/en/ecs-logging/php/current/setup.html
 navigation_title: Get started
@@ -76,6 +79,11 @@ Logs the following (multi-line formatted for better readability):
 
 ## Step 2: Configure Filebeat [setup-step-2]
 
+```{applies_to}
+stack: ga
+serverless: unavailable
+```
+
 :::::::{tab-set}
 
 ::::::{tab-item} Log file