docs(ads): expand call_to_action_type enum list in create_ad_creative (#99)

Free-form CTA values (e.g. MAKE_RESERVATION, BOOK_TABLE) are rejected by Meta with code 100. The previous docstring listed only four examples, which left the LLM guessing at the right enum value for restaurants and similar verticals.

Expands the docstring with the documented set of common Meta CTA values and explicitly notes that BOOK_NOW is the correct choice for restaurant reservations / appointments.

Doc-only change. No behavior change.

Author: nictuku

meta_ads_mcp/core/ads.py

@@ -1625,8 +1625,16 @@ async def create_ad_creative(
                             to serve different aspect ratios per placement (e.g., 1:1 Feed + 9:16 Reels).
                           Other values are passed through to Meta as-is.
         dynamic_creative_spec: Dynamic creative optimization settings
-        call_to_action_type: Call to action button type (e.g., 'LEARN_MORE', 'SIGN_UP', 'SHOP_NOW',
-                            'CALL_NOW'). When using CALL_NOW, also provide phone_number.
+        call_to_action_type: Call to action button type. Meta enum — free-form values
+                            (e.g. 'MAKE_RESERVATION', 'RESERVE', 'BOOK_TABLE') are rejected with
+                            code 100. Pick from the documented list. Common values:
+                              BOOK_NOW         — restaurants, salons, clinics, appointments (use this for
+                                                 reservations — there is no MAKE_RESERVATION enum)
+                              LEARN_MORE, SHOP_NOW, SIGN_UP, SUBSCRIBE, GET_QUOTE, CONTACT_US,
+                              DOWNLOAD, WATCH_MORE, GET_OFFER, APPLY_NOW, CALL_NOW, MESSAGE_PAGE,
+                              SEE_MENU, ORDER_NOW, BUY_NOW, WHATSAPP_MESSAGE, GET_DIRECTIONS,
+                              BUY_TICKETS, EVENT_RSVP, BOOK_TRAVEL.
+                            When using CALL_NOW, also provide phone_number.
         lead_gen_form_id: Lead generation form ID for lead generation campaigns. Required when using
                          lead generation CTAs like 'SIGN_UP', 'GET_OFFER', 'SUBSCRIBE', etc.
         instagram_actor_id: Instagram account ID for Instagram placements (must be a string