perf(tiles): filter trails by length_m per zoom level

- z<=7: min 2000m, limit 3000
- z==8: min 500m,  limit 8000
- z==9: min 200m,  limit 8000
- z==10: min 50m,  limit 15000
- z>=11: no filter, limit 25000

Reduces row count from 25k to ~hundreds on z8 tiles.

tasks/enduro-trails/prototype/app.py

@@ -252,14 +252,26 @@ async def get_tile(z: int, x: int, y: int):
     q_north = north + buf_y
 
     if z <= 7:
-        limit = 5000
+        limit = 3000
     elif z <= 9:
-        limit = 25000
+        limit = 8000
     elif z <= 11:
-        limit = 25000
+        limit = 15000
     else:
         limit = 25000
 
+    # Минимальная длина трека по зуму — фильтруем мусор на низких зумах
+    if z <= 7:
+        min_length = 2000
+    elif z == 8:
+        min_length = 500
+    elif z == 9:
+        min_length = 200
+    elif z == 10:
+        min_length = 50
+    else:
+        min_length = 0
+
     try:
         conn = get_db()
         cur = conn.cursor()
@@ -269,8 +281,9 @@ async def get_tile(z: int, x: int, y: int):
             FROM trails
             WHERE min_lon <= ? AND max_lon >= ?
               AND min_lat <= ? AND max_lat >= ?
+              AND (length_m >= ? OR length_m IS NULL)
             LIMIT ?
-        """, (q_east, q_west, q_north, q_south, limit))
+        """, (q_east, q_west, q_north, q_south, min_length, limit))
         trails_rows = cur.fetchall()
 
         cur.execute("""