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>

alert/flat.py

@@ -27,7 +27,6 @@ class Flat:
         self.raw_data = data
         self.id = self.link  # we could use data.get('id', None) but link is easier to debug
         self.gmaps = maps.Maps()
-        self._connectivity = None
         self._coords = None
         self.address_link_gmaps = f"https://www.google.com/maps/search/?api=1&query={quote(self.address)}"
 
@@ -54,24 +53,8 @@ class Flat:
             return self.total_rent / self.size
         return 0.0
 
-    @property
-    def connectivity(self):
-        if not self._connectivity:
-            self._connectivity = self.gmaps.calculate_score(self.address)
-        return self._connectivity
-
     @property
     def coords(self):
         if self._coords is None:
             self._coords = self.gmaps.geocode(self.address) or (None, None)
         return self._coords
-
-    @property
-    def display_address(self):
-        if ',' in self.address:
-            parts = self.address.split(',', 1)
-            street_part = parts[0].strip()
-            city_part = parts[1].replace(',', '').strip()
-            return f"{street_part}\n{city_part}"
-        else:
-            return self.address