fix(medications): read the dose history's window, not every intake

The history tab asks for a window of at most a year, but the route read
every intake the medication ever had: a medication taken three times a
day for five years read about 5,500 rows on each open. The full read
also served to find the last intake for rolling cadences.

The route now reads the rows anchored or taken in the window, and of
the rows before it only the latest take, which is the anchor a rolling
grid re-starts from and the last intake when none falls in the window.
Earlier takes place no slot in the window, so the ledger is the same.
The read moves into its own function, which shortens the handler.

src/__tests__/baselines/source-function-lines.json

@@ -1,7 +1,7 @@
 {
   "$comment": "Production functions over 200 lines, keyed \"file :: name\", and their length. Maintained by src/__tests__/source-size-ratchet.test.ts.",
   "count": 339,
-  "total": 110080,
+  "total": 110065,
   "entries": {
     "app/achievements/page.tsx :: AchievementsPage": 206,
     "app/api/admin/backups/upload/route.ts :: apiHandler(arg)": 275,
@@ -27,7 +27,7 @@
     "app/api/mcp/oauth/token/route.ts :: POST": 250,
     "app/api/mcp/oauth/token/route.ts :: POST > withBackgroundEvent(arg)": 248,
     "app/api/measurement-reminders/[id]/route.ts :: apiHandler(arg) #2": 239,
-    "app/api/medications/[id]/dose-history/route.ts :: apiHandler(arg)": 256,
+    "app/api/medications/[id]/dose-history/route.ts :: apiHandler(arg)": 241,
     "app/api/medications/[id]/inventory/[itemId]/route.ts :: apiHandler(arg)": 204,
     "app/api/medications/[id]/schedule-revisions/[revisionId]/route.ts :: apiHandler(arg)": 250,
     "app/api/mental-health/assessments/route.ts :: postAssessment": 249,