feat: Phase 4 grouping with entry-break dividers

Add group.py route, phase4.html template, and supporting state changes.
Photos are shown as a flat stream; clicking divider zones inserts
entry-break boundaries that split photos into labelled groups. Labels
persist via group_labels dict. Done materialises groups into state.groups
and advances to write phase.

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

services/travel-memories/app/__init__.py

@@ -8,13 +8,14 @@ def create_app(state_dir=None, pages_dir=None):
     app.config["IMMICH_URL"] = os.environ.get("IMMICH_URL", "")
     app.config["IMMICH_API_KEY"] = os.environ.get("IMMICH_API_KEY", "")
 
-    from .routes import albums, triage, proxy, notes, nav, curate
+    from .routes import albums, triage, proxy, notes, nav, curate, group
     app.register_blueprint(albums.bp)
     app.register_blueprint(triage.bp)
     app.register_blueprint(proxy.bp)
     app.register_blueprint(notes.bp)
     app.register_blueprint(nav.bp)
     app.register_blueprint(curate.bp)
+    app.register_blueprint(group.bp)
 
     @app.get("/health")
     def health():