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>

README.md

@@ -1,4 +1,4 @@
-# lazyflat
+# wohnungsdidi
 
 Combined deployment of **flat-alert** (reliable scraper) and **flat-apply**
 (experimental auto‑applier) behind a single authenticated web UI.
@@ -51,7 +51,7 @@ Because `apply/` is still experimental, the system is hardened around it:
 
 ## Deployment on Coolify
 
-1. **Create repo**: push this monorepo to `ssh://git@git.moritz.run:2222/moritz/lazyflat.git`.
+1. **Create repo**: push this monorepo to `ssh://git@git.moritz.run:2222/moritz/wohnungsdidi.git`.
 2. **New Coolify resource** → *Docker Compose* → point it at this repo. Coolify
    will read `docker-compose.yml` and deploy all three services on one network.
 3. **Domain**: set `flat.lab.moritz.run` on the `web` service only. Coolify