feat(journal): /api/journal/* routes blueprint + cosine helper unit tests

Endpoints:
- GET/PUT /api/journal/config — per-user journal config
- GET /api/journal/today — today's journal conversation, generates daily prep on demand
- GET /api/journal/day/<iso_date> — past day's journal
- GET /api/journal/days — list of dates with journal content
- POST /api/journal/trigger-prep — manual regeneration of prep
- GET /api/journal/moments — list/search moments with filters
- PATCH /api/journal/moments/<id> — edit content/tags/pinned + junctions
- DELETE /api/journal/moments/<id>

Blueprint registered in app.py.
tests/test_journal_search.py — cosine helper coverage.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/fabledassistant/app.py

@@ -12,6 +12,7 @@ from fabledassistant.routes.admin import admin_bp
 from fabledassistant.routes.api import api
 from fabledassistant.routes.auth import auth_bp
 from fabledassistant.routes.chat import chat_bp
+from fabledassistant.routes.journal import journal_bp
 from fabledassistant.routes.export import export_bp
 from fabledassistant.routes.notes import notes_bp
 from fabledassistant.routes.images import images_bp
@@ -75,6 +76,7 @@ def create_app() -> Quart:
     app.register_blueprint(api)
     app.register_blueprint(auth_bp)
     app.register_blueprint(chat_bp)
+    app.register_blueprint(journal_bp)
     app.register_blueprint(export_bp)
     app.register_blueprint(images_bp)
     app.register_blueprint(milestones_bp)