add journaling feature: categories, tags, attachments, calendar, and multi-select emotions

Adds an 8th development stage that lets users keep a free-form journal alongside
habit tracking, reusing the existing Google OAuth/DB/PWA infrastructure instead
of a separate project. Users organize entries into custom categories, filter by
a month calendar with day-detail drill-down, attach photos/videos (served via an
authenticated route, never /static), tag entries, and pick multiple emotions per
entry from a curated 9-option set. Includes a global journal prompt bank for
lightweight guided journaling.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/config.py

@@ -18,5 +18,8 @@ class Settings(BaseSettings):
     session_cookie_name: str = "habit_session"
     timezone: str = "Asia/Seoul"
 
+    journal_media_root: str = "app/media/journal"
+    journal_max_upload_mb: int = 20
+
 
 settings = Settings()