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>

web/settings.py

@@ -25,7 +25,7 @@ AUTH_PASSWORD_HASH: str = _required("AUTH_PASSWORD_HASH")
 
 # --- Session cookie -----------------------------------------------------------
 SESSION_SECRET: str = getenv("SESSION_SECRET") or secrets.token_urlsafe(48)
-SESSION_COOKIE_NAME: str = "lazyflat_session"
+SESSION_COOKIE_NAME: str = "wohnungsdidi_session"
 SESSION_MAX_AGE_SECONDS: int = int(getenv("SESSION_MAX_AGE_SECONDS", str(60 * 60 * 24 * 7)))
 COOKIE_SECURE: bool = getenv("COOKIE_SECURE", "true").lower() in ("true", "1", "yes", "on")
 
@@ -43,6 +43,8 @@ ALERT_SCRAPE_INTERVAL_SECONDS: int = int(getenv("ALERT_SCRAPE_INTERVAL_SECONDS",
 # --- Storage ------------------------------------------------------------------
 DATA_DIR: Path = Path(getenv("DATA_DIR", "/data"))
 DATA_DIR.mkdir(parents=True, exist_ok=True)
+# Legacy filename — kept so existing data under /data/lazyflat.sqlite stays
+# reachable across the rename to wohnungsdidi. Not user-facing.
 DB_PATH: Path = DATA_DIR / "lazyflat.sqlite"
 
 # Retention (errors / audit / application forensics). Default 14 days.
@@ -58,7 +60,7 @@ SMTP_HOST: str = getenv("SMTP_HOST", "")
 SMTP_PORT: int = int(getenv("SMTP_PORT", "587"))
 SMTP_USERNAME: str = getenv("SMTP_USERNAME", "")
 SMTP_PASSWORD: str = getenv("SMTP_PASSWORD", "")
-SMTP_FROM: str = getenv("SMTP_FROM", "lazyflat@localhost")
+SMTP_FROM: str = getenv("SMTP_FROM", "wohnungsdidi@localhost")
 SMTP_STARTTLS: bool = getenv("SMTP_STARTTLS", "true").lower() in ("true", "1", "yes", "on")
 
 # --- App URL (used to build links in notifications) ---------------------------