SegmentCreate: prompt after save instead of immediate redirect; update plan

After saving, show "Saved! Add another from this activity?" with two
buttons: "Add another" (resets name/handles, keeps map loaded) and
"Done" (navigates to /segments/).

site/src/components/SegmentCreate.svelte

@@ -29,6 +29,8 @@
   let segSport = '';
   let saving = false;
   let saveError = '';
+  let justSaved = false;
+  let lastSavedName = '';
 
   // ── Map ───────────────────────────────────────────────────────────────────
   let mapEl: HTMLDivElement;
@@ -251,14 +253,29 @@
         }),
       });
       const d = await r.json();
-      if (r.ok) { window.location.href = `${base}segments/`; }
-      else { saveError = d.detail ?? 'Failed to save segment'; saving = false; }
+      if (r.ok) {
+        lastSavedName = segName.trim();
+        justSaved = true;
+        saving = false;
+      } else {
+        saveError = d.detail ?? 'Failed to save segment';
+        saving = false;
+      }
     } catch {
       saveError = 'Could not reach server';
       saving = false;
     }
   }
 
+  function addAnother() {
+    justSaved = false;
+    segName = '';
+    segSport = selectedActivity?.sport ?? '';
+    startIdx = 0;
+    endIdx = maxIdx;
+    saveError = '';
+  }
+
   // ── Helpers ───────────────────────────────────────────────────────────────
   function polylineDistance(pts: [number, number][]): number {
     let d = 0;
@@ -406,17 +423,36 @@
         </select>
       </div>
 
-      {#if saveError}
-        <p class="text-red-400 text-sm mb-3">{saveError}</p>
-      {/if}
+      {#if justSaved}
+        <div class="rounded-lg bg-zinc-800 border border-zinc-700 px-4 py-3 flex flex-col gap-3">
+          <p class="text-sm text-white">
+            <span class="text-green-400 font-medium">✓ "{lastSavedName}" saved.</span>
+            Add another segment from this activity?
+          </p>
+          <div class="flex gap-2">
+            <button
+              on:click={addAnother}
+              class="flex-1 py-2 rounded-lg text-sm font-medium bg-blue-600 hover:bg-blue-500 text-white transition-colors"
+            >Add another</button>
+            <a
+              href="{base}segments/"
+              class="flex-1 py-2 rounded-lg text-sm font-medium text-center bg-zinc-700 hover:bg-zinc-600 text-white transition-colors"
+            >Done</a>
+          </div>
+        </div>
+      {:else}
+        {#if saveError}
+          <p class="text-red-400 text-sm mb-3">{saveError}</p>
+        {/if}
 
-      <button
-        on:click={save}
-        disabled={!canSave}
-        class="w-full py-2.5 rounded-lg text-sm font-medium transition-colors
-               bg-blue-600 hover:bg-blue-500 text-white
-               disabled:opacity-40 disabled:cursor-not-allowed"
-      >{saving ? 'Saving…' : 'Save segment'}</button>
+        <button
+          on:click={save}
+          disabled={!canSave}
+          class="w-full py-2.5 rounded-lg text-sm font-medium transition-colors
+                 bg-blue-600 hover:bg-blue-500 text-white
+                 disabled:opacity-40 disabled:cursor-not-allowed"
+        >{saving ? 'Saving…' : 'Save segment'}</button>
+      {/if}
     {/if}
   {/if}
 </div>