rename to wohnungsdidi + didi logo + footer for all + seconds-only counter

- App is now called "wohnungsdidi" everywhere user-facing (page title,
  nav brand, login header, notification subjects, report filename,
  FastAPI titles, log messages)
- Brand dot replaced with an image of Didi (web/static/didi.webp),
  rendered as a round 2.25rem avatar in _layout + login
- "Programmiert für Annika ♥" footer now shows for every logged-in user,
  not only Annika
- Count-up shows only seconds ("vor 73 s") regardless of age — no
  rollover to minutes/hours
- Data continuity: DB file stays /data/lazyflat.sqlite and the Docker
  volume stays lazyflat_data so the rename doesn't strand existing data
- Session cookie renamed to wohnungsdidi_session (one-time logout on
  rollout)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -1,7 +1,7 @@
 services:
   web:
     build: ./web
-    container_name: lazyflat-web
+    container_name: wohnungsdidi-web
     restart: unless-stopped
     depends_on:
       apply:
@@ -26,18 +26,20 @@ services:
       - SMTP_PORT=${SMTP_PORT:-587}
       - SMTP_USERNAME=${SMTP_USERNAME:-}
       - SMTP_PASSWORD=${SMTP_PASSWORD:-}
-      - SMTP_FROM=${SMTP_FROM:-lazyflat@localhost}
+      - SMTP_FROM=${SMTP_FROM:-wohnungsdidi@localhost}
       - SMTP_STARTTLS=${SMTP_STARTTLS:-true}
       - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY:-}
       - ANTHROPIC_MODEL=${ANTHROPIC_MODEL:-claude-haiku-4-5-20251001}
     volumes:
+      # Legacy volume name — kept so Coolify reuses the existing data volume
+      # after the rename from lazyflat → wohnungsdidi.
       - lazyflat_data:/data
     expose:
       - "8000"
 
   apply:
     build: ./apply
-    container_name: lazyflat-apply
+    container_name: wohnungsdidi-apply
     restart: unless-stopped
     expose:
       - "8000"
@@ -51,7 +53,7 @@ services:
 
   alert:
     build: ./alert
-    container_name: lazyflat-alert
+    container_name: wohnungsdidi-alert
     restart: unless-stopped
     depends_on:
       web: