perf(library): one dashboard call, stored game detail first

The Dashboard loads the top and playing tiles from
GET /api/library/dashboard-games in one call. The game page shows the
stored game first (refresh=false) and calls again only when
achievementsStale is true. The second answer merges the achievement
fields; it takes status and finishedHint only when the user did not
change the status. The points check runs again after the refresh.

Refs #47

README.md

@@ -21,7 +21,7 @@ To Be Played is split into three repositories:
 
 - **Dashboard** with an edit mode ("Customize"): the user orders, hides and resizes the tiles (small = half width
   and less content, large = double width and more), and can add the stat groups of "Your stats" as tiles. Stored
-  in Auth, so it follows the user to the phone; "Reset" goes back to the default. Tiles: most played games, games in progress, "Pile of Shame" with backlog hours, its trend of the last 90
+  in Auth, so it follows the user to the phone; "Reset" goes back to the default. Tiles: most played games and games in progress (one call, `GET /api/library/dashboard-games`), "Pile of Shame" with backlog hours, its trend of the last 90
   days ("this month: +N added, -N off the pile") and a random suggestion,
   Steam avatar and a banner from the most played game of the last two weeks, and an achievement card: unlocked
   total, perfect games, average completion and the 5 games closest to 100 %. The card counts PlayStation trophies too
@@ -118,7 +118,7 @@ flowchart LR
   a hidden trophy shows "Hidden trophy" until it is earned; a set whose list is not stored yet says it loads with the
   next sync. The sync banner and inbox text say "achievements or trophies". Library tiles show the best set of a game.
   The sync details list games whose last achievement this sync unlocked, with a button to set them to 100 %.
-- **Game detail**: status, priority, 1–5 star rating, notes, achievements, time to beat (story / extras / 100 %),
+- **Game detail**: the page shows the stored game at once (`?refresh=false`); when Core says `achievementsStale` a second call refreshes the achievements from Steam and replaces the data. Status, priority, 1–5 star rating, notes, achievements, time to beat (story / extras / 100 %),
   a link to the game's speedrun.com page when it has verified runs, a hint when Steam shows recent playtime for a
   game still in the backlog, and one to set the status to 100 % when
   every achievement is unlocked.
@@ -295,7 +295,7 @@ flowchart LR
 
 ```mermaid
 flowchart LR
-    DetailData["Core GET /api/library/games/{appid}: platforms[] + totalPlaytimeMinutes"] --> Platforms["PlatformsCard: row per platform, total"]
+    DetailData["Core GET /api/library/games/{appid}?refresh=false, then without it when achievementsStale: platforms[] + totalPlaytimeMinutes"] --> Platforms["PlatformsCard: row per platform, total"]
     DetailData --> Hero["GameHeroCard: total playtime"]
     Platforms -->|"row of another edition"| Other["/library/{appid} of that edition"]
 ```