feat: raise cache default to 100K entries, evict stalest instead of dropping

The 10K cap was too conservative — the blocklist alone holds 400K domains.
At ~100 bytes per wire entry, 100K entries is ~10MB.

When the cache is full and evict_expired doesn't free enough slots,
evict_stalest removes the entry with the least remaining TTL instead of
silently discarding the new insert.

src/config.rs

@@ -302,7 +302,7 @@ impl Default for CacheConfig {
 }
 
 fn default_max_entries() -> usize {
-    10000
+    100_000
 }
 fn default_min_ttl() -> u32 {
     60