Raise the bloom antipoison FPR cap default to 0.20

The inbound FilterAnnounce cap at 0.10 rejects aggregates that are
legitimately near their operating ceiling, before the network reaches
the fixed-filter capacity limit. Raise the default to 0.20, which
corresponds to fill 0.7248 at k=5, about 2,114 entries on the 1 KB
filter (Swamidass-Baldi).

Also remove the duplicate default definitions in BloomConfig. Each
default was written twice, once in impl Default and once in the serde
default function, with nothing enforcing that they agree, so a config
file that omits the key took a different path from one that sets it.
impl Default now delegates to the serde default functions, leaving a
single source of truth.

src/config/node.rs

@@ -635,8 +635,8 @@ pub struct BloomConfig {
     pub update_debounce_ms: u64,
     /// Antipoison cap: reject inbound FilterAnnounce whose FPR exceeds
     /// this value (`node.bloom.max_inbound_fpr`). Valid range `(0.0, 1.0)`.
-    /// Default `0.10` ≈ fill 0.631 at k=5 ≈ ~1,630 entries on the 1 KB
-    /// filter (Swamidass–Baldi). Raised from 0.05 so aggregates that are
+    /// Default `0.20` ≈ fill 0.7248 at k=5 ≈ ~2,114 entries on the 1 KB
+    /// filter (Swamidass–Baldi). Raised from 0.10 so aggregates that are
     /// legitimately near their operating ceiling are not rejected before
     /// the network reaches the fixed-filter capacity limit; conceptually
     /// distinct from future autoscaling hysteresis setpoints — same unit,
@@ -648,8 +648,8 @@ pub struct BloomConfig {
 impl Default for BloomConfig {
     fn default() -> Self {
         Self {
-            update_debounce_ms: 500,
-            max_inbound_fpr: 0.10,
+            update_debounce_ms: Self::default_update_debounce_ms(),
+            max_inbound_fpr: Self::default_max_inbound_fpr(),
         }
     }
 }
@@ -659,7 +659,7 @@ impl BloomConfig {
         500
     }
     fn default_max_inbound_fpr() -> f64 {
-        0.10
+        0.20
     }
 }