Add configurable pace-artifact filtering to replace the hardcoded cutoff

Two new Profile settings -- "minimum representative pace" and "minimum
representative time" -- replace the previous hardcoded 20:00/km cutoff. A
stretch of consecutive samples slower than the configured pace is now
dropped from the chart (and its Y-axis scale) only if it lasts no longer
than the configured time; a longer stretch is kept as a real stop or walk
break rather than noise. Defaults to 12:00/km and 3 seconds.

Caught a boundary bug while verifying against real data: a run lasting
exactly the threshold duration survived filtering because the comparison
used strict "<" instead of "<=", contradicting "not lasting more than N
seconds" (which should include exactly N).

frontend/src/pages/Profile.tsx

@@ -26,6 +26,56 @@ function NumberField({
   );
 }
 
+// Pace is entered/displayed as "m:ss" but stored as whole seconds.
+function parsePace(text: string): number | null {
+  const trimmed = text.trim();
+  if (trimmed === "") return null;
+  const match = /^(\d+):([0-5]?\d)$/.exec(trimmed);
+  if (!match) return null;
+  return Number(match[1]) * 60 + Number(match[2]);
+}
+
+function formatPace(seconds: number): string {
+  const m = Math.floor(seconds / 60);
+  const s = Math.round(seconds % 60);
+  return `${m}:${s.toString().padStart(2, "0")}`;
+}
+
+function PaceField({
+  label,
+  value,
+  onChange,
+}: {
+  label: string;
+  value: number;
+  onChange: (v: number) => void;
+}) {
+  const [text, setText] = useState(formatPace(value));
+  useEffect(() => setText(formatPace(value)), [value]);
+
+  function commit(raw: string) {
+    const parsed = parsePace(raw);
+    if (parsed != null) {
+      onChange(parsed);
+    } else {
+      setText(formatPace(value)); // invalid input -- revert to the last valid value
+    }
+  }
+
+  return (
+    <label>
+      {label}
+      <input
+        type="text"
+        value={text}
+        onChange={(e) => setText(e.target.value)}
+        onBlur={(e) => commit(e.target.value)}
+        placeholder="12:00"
+      />
+    </label>
+  );
+}
+
 function NullableNumberField({
   label,
   value,
@@ -178,6 +228,27 @@ export function Profile() {
         </p>
       </fieldset>
 
+      <fieldset className="kind-editor">
+        <legend>Pace chart artifacts</legend>
+        <div className="controls">
+          <PaceField
+            label="Minimum representative pace (m:ss/km)"
+            value={profile.MinRepresentativePaceSecPerKm}
+            onChange={(v) => set("MinRepresentativePaceSecPerKm", v)}
+          />
+          <NumberField
+            label="Minimum representative time (seconds)"
+            value={profile.MinRepresentativeTimeSeconds}
+            onChange={(v) => set("MinRepresentativeTimeSeconds", v)}
+          />
+        </div>
+        <p className="empty-state">
+          A stretch of samples slower than this pace is hidden from the Review Queue's pace chart (and doesn't stretch
+          its scale) unless it lasts at least this long -- e.g. a brief GPS blip right as recording starts gets
+          dropped, but a real walk break or stop is kept.
+        </p>
+      </fieldset>
+
       <button onClick={save}>Save</button>
     </div>
   );

frontend/src/pages/ReviewQueue.tsx

@@ -2,7 +2,7 @@ import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { api } from "../api/client";
 import { ExpectedVsActualChart } from "../components/charts/ExpectedVsActualChart";
 import { RawDataModal } from "../components/RawDataModal";
-import type { ReviewQueueItem, ScoredKind, WorkoutKind } from "../types/api";
+import type { Profile, ReviewQueueItem, ScoredKind, WorkoutKind } from "../types/api";
 
 const UNSORTED = "__unsorted__";
 const PAGE_SIZE = 10;
@@ -30,6 +30,7 @@ export function ReviewQueue() {
   const [initialLoading, setInitialLoading] = useState(true);
   const [loadingMore, setLoadingMore] = useState(false);
   const [kinds, setKinds] = useState<WorkoutKind[]>([]);
+  const [profile, setProfile] = useState<Profile | null>(null);
   const [filterKindId, setFilterKindId] = useState<string>("");
   const [error, setError] = useState<string | null>(null);
   const [resolvingId, setResolvingId] = useState<number | null>(null);
@@ -89,13 +90,14 @@ export function ReviewQueue() {
   function reload() {
     setItems([]);
     setInitialLoading(true);
-    Promise.all([api.reviewQueue({ limit: PAGE_SIZE }), api.listWorkoutKinds()])
-      .then(([page, workoutKinds]) => {
+    Promise.all([api.reviewQueue({ limit: PAGE_SIZE }), api.listWorkoutKinds(), api.getProfile()])
+      .then(([page, workoutKinds, userProfile]) => {
         nextCursorRef.current = page.next_cursor;
         setItems(page.items);
         setNextCursor(page.next_cursor);
         setTotal(page.total);
         setKinds(workoutKinds);
+        setProfile(userProfile);
       })
       .catch((e) => setError(String(e)))
       .finally(() => setInitialLoading(false));
@@ -217,7 +219,12 @@ export function ReviewQueue() {
                   </p>
                 )}
 
-                <ExpectedVsActualChart laps={item.laps} samples={item.samples} />
+                <ExpectedVsActualChart
+                  laps={item.laps}
+                  samples={item.samples}
+                  minRepresentativePaceSecPerKm={profile?.MinRepresentativePaceSecPerKm ?? 0}
+                  minRepresentativeTimeSeconds={profile?.MinRepresentativeTimeSeconds ?? 0}
+                />
 
                 <div className="review-item-actions">
                   {manuallyAssignableKinds.map((k) => (