frontend: date range picker on Incidents and Archive; fix Archive paging

Incidents and Archive get a from/to date range (native date inputs,
local-day bounds). Incidents filters in the Firestore query; Archive
passes date_from/date_to to GET /calls/search, which applies them as a
started_at range — both ride the existing org_id/started_at index.

Also fixes /calls/search and /calls/eval-queue paging: the cursor went to
Firestore as a raw ISO string against a timestamp field, which compares
by type rather than time, so "Load more" re-read the first page. Cursor
and range bounds are now parsed to datetimes (400 on garbage).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-c2-core/app/routers/calls.py

@@ -23,6 +23,23 @@ class EvalTranscriptUpdate(BaseModel):
 router = APIRouter(prefix="/calls", tags=["calls"])
 
 
+def _parse_ts(value: Optional[str], field: str) -> Optional[datetime]:
+    """ISO string from a query param → aware datetime, or 400.
+
+    started_at is stored as a Firestore timestamp, so a cursor or range bound
+    passed through as the raw string compares by *type* (every string sorts
+    after every timestamp) rather than by time — a string cursor made "Load
+    more" return the first page again.
+    """
+    if not value:
+        return None
+    try:
+        dt = datetime.fromisoformat(value.replace("Z", "+00:00"))
+    except ValueError:
+        raise HTTPException(400, f"{field} is not an ISO-8601 timestamp.")
+    return dt if dt.tzinfo else dt.replace(tzinfo=timezone.utc)
+
+
 @router.get("")
 async def list_calls(
     node_id: Optional[str] = Query(None),
@@ -55,6 +72,8 @@ async def search_calls(
     link: str = Query("any", pattern="^(any|orphan|linked)$"),
     transcript: str = Query("any", pattern="^(any|yes|no)$"),
     q: Optional[str] = Query(None, description="case-insensitive substring of the transcript"),
+    date_from: Optional[str] = Query(None, description="ISO timestamp, inclusive lower bound on started_at"),
+    date_to: Optional[str] = Query(None, description="ISO timestamp, inclusive upper bound on started_at"),
     decoded: dict = Depends(require_firebase_token),
 ):
     """
@@ -88,13 +107,24 @@ async def search_calls(
     if not org_id:
         raise HTTPException(403, "No organization scope for this caller.")
 
+    cursor_dt = _parse_ts(cursor, "cursor")
+    from_dt = _parse_ts(date_from, "date_from")
+    to_dt = _parse_ts(date_to, "date_to")
+
+    # A range on the ordered field rides the same org_id/started_at index.
+    conditions: list[tuple[str, str, object]] = [("org_id", "==", org_id)]
+    if from_dt:
+        conditions.append(("started_at", ">=", from_dt))
+    if to_dt:
+        conditions.append(("started_at", "<=", to_dt))
+
     window = max(limit * 10, 200)
     rows = await fstore.collection_where(
         "calls",
-        [("org_id", "==", org_id)],
+        conditions,
         order_by=[("started_at", "DESCENDING")],
         limit_to=window,
-        start_after={"started_at": cursor} if cursor else None,
+        start_after={"started_at": cursor_dt} if cursor_dt else None,
     )
 
     needle = (q or "").strip().lower()
@@ -169,13 +199,14 @@ async def eval_queue(
     if not org_id:
         raise HTTPException(403, "No organization scope for this caller.")
 
+    cursor_dt = _parse_ts(cursor, "cursor")
     window = max(limit * 20, 300)
     rows = await fstore.collection_where(
         "calls",
         [("org_id", "==", org_id)],
         order_by=[("started_at", "DESCENDING")],
         limit_to=window,
-        start_after={"started_at": cursor} if cursor else None,
+        start_after={"started_at": cursor_dt} if cursor_dt else None,
     )
 
     def _eligible(c: dict) -> bool: