refactor: remove completed one-time startup migrations

Production data is migrated and every marker is recorded in the system
collection, so the stock dividend-history, sticker legacy-pack and stats
stock_dividend migrations no longer do anything. Stats keeps its startup
index creation and still hides retired stock_dividend rows.

docs/deploy-coolify-selfhosted.md

@@ -149,13 +149,9 @@ MP4, with the same text fallback.
 - **`coin`** stores cash as `usd` and embeds positions as
   `assets.<symbol>.{quantity,base}`.
 - **`system`** holds one marker per completed one-time startup migration. Keep
-  those records as audit history. The current markers are
-  `migration:stats-delete-stock-dividend-v1` (retires historical
-  `/stock_dividend` stats rows without erasing them),
-  `migration:stock-dividend-history-v1` (removes the retired dividend cursor
-  and hashed applied-event ledger), and
-  `migration:sticker-drop-legacy-packs-v1` (removes records left by the retired
-  per-user sticker pack commands).
+  those records as audit history. No one-time migration runs at startup now;
+  the completed ones were removed from the code once production data was
+  verified migrated.
 
 ## 2. Coolify
 

docs/sticker-packs.md

@@ -6,12 +6,7 @@ storage, and no per-user packs.
 
 **The module stores nothing.** Its factory ignores the collection it is handed:
 the pack comes from the environment and the set owner from `OWNER_ID`, so there
-is nothing per-user to key. A one-time startup cleanup
-(`migration:sticker-drop-legacy-packs-v1`) removes the records the retired
-per-user pack commands left in the `sticker` collection — pack documents keyed
-by owner ID, `slug:` name reservations, and `pending-delete:` confirmations.
-It is marker-guarded, so it scans once per database and never touches anything
-written afterwards.
+is nothing per-user to key.
 
 | Command | Parameters | Reply to | What it does |
 |---|---|---|---|