feat: add base shell, notes panel, back-navigation with stale propagation

Implements Task 4: base.html DaisyUI/Alpine shell, notes autosave panel,
nav.py phase switching with downstream stale marking, notes.py save/get
endpoints, state debug endpoint, and stub /triage route for test support.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/travel-memories/app/routes/albums.py

@@ -1,3 +1,23 @@
-from flask import Blueprint
+from flask import Blueprint, current_app, render_template, request
+from app.state import load_state
 
 bp = Blueprint("albums", __name__)
+
+
+@bp.get("/triage")
+def triage():
+    album_id = request.args.get("album_id", "")
+    notes_content = ""
+    phase_stale = []
+    if album_id:
+        state = load_state(album_id, current_app)
+        if state:
+            notes_content = state.notes
+            phase_stale = state.phase_stale
+    return render_template(
+        "base.html",
+        current_phase="triage",
+        album_id=album_id,
+        notes_content=notes_content,
+        phase_stale=phase_stale,
+    )