chore: sweep dead code across all three services

Per review §1 — verified no callers before each deletion:

- _next_scrape_utc (context dict key never read by any template)
- ALERT_SCRAPE_INTERVAL_SECONDS settings import (only _next_scrape_utc read it)
- alert/paths.py (imported by nothing)
- alert/settings.py LANGUAGE (alert doesn't use translations.toml)
- alert/main.py: the vestigial `c = {}` connectivity dict, the comment
  about re-enabling it, and the entire connectivity block in
  _flat_payload — the web-side columns stay NULL on insert now
- alert/maps.py: DESTINATIONS, calculate_score, _get_next_weekday,
  _calculate_transfers (only geocode is used in the scraper)
- alert/flat.py: connectivity + display_address properties,
  _connectivity field, unused datetime import
- apply/utils.py str_to_preview (no callers) — file removed
- web/matching.py: max_morning_commute + commute check
- web/app.py: don't pass connectivity dict into flat_matches_filter,
  don't write email_address through update_notifications
- web/db.py: get_error (no callers); drop kill_switch,
  max_morning_commute, email_address from their allowed-sets so they're
  not writable through update_* anymore
- web/settings.py + docker-compose.yml: SMTP_HOST/PORT/USERNAME/PASSWORD/
  FROM/STARTTLS (notifications.py is telegram-only now)

DB columns themselves (kill_switch, email_address, max_morning_commute,
connectivity_morning_time, connectivity_night_time) stay in the schema
— SQLite can't drop them cheaply and they're harmless.

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

web/app.py

@@ -53,7 +53,6 @@ from auth import (
 )
 from matching import flat_matches_filter, row_to_dict
 from settings import (
-    ALERT_SCRAPE_INTERVAL_SECONDS,
     APPLY_FAILURE_THRESHOLD,
     INTERNAL_API_KEY,
     PUBLIC_URL,
@@ -200,16 +199,6 @@ def _auto_apply_allowed(prefs) -> bool:
     return apply_client.health()
 
 
-def _next_scrape_utc() -> str:
-    hb = db.get_state("last_alert_heartbeat")
-    dt = _parse_iso(hb)
-    if dt is None:
-        return ""
-    if dt.tzinfo is None:
-        dt = dt.replace(tzinfo=timezone.utc)
-    return (dt + timedelta(seconds=ALERT_SCRAPE_INTERVAL_SECONDS)).astimezone(timezone.utc).isoformat(timespec="seconds")
-
-
 def _last_scrape_utc() -> str:
     hb = db.get_state("last_alert_heartbeat")
     dt = _parse_iso(hb)
@@ -425,7 +414,7 @@ def _wohnungen_context(user) -> dict:
                 continue
         if not flat_matches_filter({
             "rooms": f["rooms"], "total_rent": f["total_rent"], "size": f["size"],
-            "wbs": f["wbs"], "connectivity": {"morning_time": f["connectivity_morning_time"]},
+            "wbs": f["wbs"],
         }, filters):
             continue
         last = db.last_application_for_flat(uid, f["id"])
@@ -499,7 +488,6 @@ def _wohnungen_context(user) -> dict:
         "apply_allowed": allowed,
         "apply_block_reason": reason,
         "apply_reachable": apply_client.health(),
-        "next_scrape_utc": _next_scrape_utc(),
         "last_scrape_utc": _last_scrape_utc(),
         "has_running_apply": has_running,
         "poll_interval": 3 if has_running else 30,
@@ -1063,7 +1051,6 @@ async def action_notifications(request: Request, user=Depends(require_user)):
         "channel": channel,
         "telegram_bot_token": form.get("telegram_bot_token", ""),
         "telegram_chat_id": form.get("telegram_chat_id", ""),
-        "email_address": "",
         "notify_on_match": _b("notify_on_match"),
         "notify_on_apply_success": _b("notify_on_apply_success"),
         "notify_on_apply_fail": _b("notify_on_apply_fail"),