Reliability improvements: retry logic, validation, ratings sync

- Add 3-attempt retry with exponential backoff to Sreality, Realingo,
  Bezrealitky, and PSN scrapers (CityHome and iDNES already had it)
- Add shared validate_listing() in scraper_stats.py; all 6 scrapers now
  validate GPS bounds, price, area, and required fields before output
- Wire ratings to server /api/ratings on page load (merge with
  localStorage) and save (async POST); ratings now persist across
  browsers and devices
- Namespace JS hash IDs as {source}_{id} to prevent rating collisions
  between listings from different portals with the same numeric ID
- Replace manual Czech diacritic table with unicodedata.normalize()
  in merge_and_map.py for correct deduplication of all edge cases
- Correct README schedule docs: every 4 hours, not twice daily

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scrape_and_map.py

@@ -15,7 +15,7 @@ import urllib.request
 import urllib.parse
 from datetime import datetime, timedelta
 from pathlib import Path
-from scraper_stats import write_stats
+from scraper_stats import write_stats, validate_listing
 
 STATS_FILE = "stats_sreality.json"
 
@@ -45,19 +45,26 @@ HEADERS = {
 
 
 def api_get(url: str) -> dict:
-    """Fetch JSON from Sreality API."""
-    logger.debug(f"HTTP GET request: {url}")
-    logger.debug(f"Headers: {HEADERS}")
-    req = urllib.request.Request(url, headers=HEADERS)
-    try:
-        with urllib.request.urlopen(req, timeout=30) as resp:
-            response_data = resp.read().decode("utf-8")
-            logger.debug(f"HTTP response: status={resp.status}, size={len(response_data)} bytes")
-            logger.debug(f"Response preview: {response_data[:200]}")
-            return json.loads(response_data)
-    except (urllib.error.URLError, ConnectionError, OSError) as e:
-        logger.error(f"HTTP request failed for {url}: {e}", exc_info=True)
-        raise
+    """Fetch JSON from Sreality API with retry."""
+    for attempt in range(3):
+        logger.debug(f"HTTP GET request (attempt {attempt + 1}/3): {url}")
+        req = urllib.request.Request(url, headers=HEADERS)
+        try:
+            with urllib.request.urlopen(req, timeout=30) as resp:
+                response_data = resp.read().decode("utf-8")
+                logger.debug(f"HTTP response: status={resp.status}, size={len(response_data)} bytes")
+                logger.debug(f"Response preview: {response_data[:200]}")
+                return json.loads(response_data)
+        except urllib.error.HTTPError:
+            raise
+        except (urllib.error.URLError, ConnectionError, OSError) as e:
+            if attempt < 2:
+                wait = (attempt + 1) * 2
+                logger.warning(f"Connection error (retry {attempt + 1}/3 after {wait}s): {e}")
+                time.sleep(wait)
+            else:
+                logger.error(f"HTTP request failed after 3 attempts: {e}", exc_info=True)
+                raise
 
 
 def build_list_url(disposition: int, page: int = 1) -> str:
@@ -356,6 +363,8 @@ def scrape(max_pages: int | None = None, max_properties: int | None = None):
             "first_seen": cached.get("first_seen", datetime.now().strftime("%Y-%m-%d")) if cached else datetime.now().strftime("%Y-%m-%d"),
             "last_changed": datetime.now().strftime("%Y-%m-%d"),
         }
+        if not validate_listing(result, "sreality"):
+            continue
         results.append(result)
         details_fetched += 1
 
@@ -476,7 +485,7 @@ def generate_map(estates: list[dict], output_path: str = "mapa_bytu.html"):
         source_label = source_labels.get(source, source)
         source_color = source_colors.get(source, "#999")
 
-        hash_id = e.get("hash_id", "")
+        hash_id = f"{source}_{e.get('hash_id', '')}"
 
         first_seen = e.get("first_seen", "")
         last_changed = e.get("last_changed", "")
@@ -864,6 +873,11 @@ function loadRatings() {{
 
 function saveRatings(ratings) {{
   localStorage.setItem(RATINGS_KEY, JSON.stringify(ratings));
+  fetch('/api/ratings', {{
+    method: 'POST',
+    headers: {{'Content-Type': 'application/json'}},
+    body: JSON.stringify(ratings)
+  }}).catch(function() {{}});
 }}
 
 function addRejectStrike(marker) {{
@@ -1167,8 +1181,25 @@ function applyFilters() {{
   document.getElementById('visible-count').textContent = visible;
 }}
 
-// Initialize ratings on load
-restoreRatings();
+// Initialize ratings: load from server, merge with localStorage, then restore
+function initRatings() {{
+  var local = loadRatings();
+  fetch('/api/ratings')
+    .then(function(r) {{ return r.ok ? r.json() : null; }})
+    .then(function(server) {{
+      if (server && typeof server === 'object') {{
+        var merged = Object.assign({{}}, local, server);
+        localStorage.setItem(RATINGS_KEY, JSON.stringify(merged));
+      }}
+      restoreRatings();
+      updateRatingCounts();
+    }})
+    .catch(function() {{
+      restoreRatings();
+      updateRatingCounts();
+    }});
+}}
+initRatings();
 
 // ── Panel toggle ──────────────────────────────────────────────
 function togglePanel() {{