fix: correct Palladium chain params and sanitize branding

- bitcoin/chainparams.c:
  - Fix mainnet RPC port 2333 → 2332 (was the P2P port)
  - Fix regtest RPC port 28444 → 12443 (verified against palladiumcore)
  - Add missing testnet entry (tplm, RPC 12332, P2P 19735, P2PKH 127/P2SH 115)
  - Reset when_lightning_became_cool to 1 (no Bitcoin-specific block reference)
  - Add operational notes: Resilience Fork at block 340,000 (2 min blocks),
    Taproot via BIP9 on mainnet / ALWAYS_ACTIVE on regtest

- common/configdir.c:
  - Fix --network help text to list palladium/testnet/regtest
  - Fix --mainnet alias description (bitcoin → palladium)

- configure: make lowdown optional (warning, not fatal); only needed for man pages

- lightningd/: replace all remaining "bitcoind/bitcoin network" log messages
  with "palladiumd/palladium network" (dual_open_control.c, opening_control.c,
  peer_htlcs.c)

- .gitignore: add ccan/config.h.* (PIDs left by build system)

common/configdir.c

@@ -340,8 +340,8 @@ struct configvar **initial_config_opts(const tal_t *ctx,
 			       "Set base directory: network-specific subdirectory is under here");
 	opt_register_early_arg("--network", opt_set_network, opt_show_network,
 			       NULL,
-			       "Select the network parameters (bitcoin, testnet,"
-			       " signet, or regtest)");
+			       "Select the network parameters (palladium, testnet,"
+			       " or regtest)");
 	opt_register_early_noarg("--testnet",
 				 opt_set_specific_network, "testnet",
 				 "Alias for --network=testnet");
@@ -353,7 +353,7 @@ struct configvar **initial_config_opts(const tal_t *ctx,
 				 "Alias for --network=signet");
 	opt_register_early_noarg("--mainnet",
 				 opt_set_specific_network, "palladium",
-				 "Alias for --network=bitcoin");
+				 "Alias for --network=palladium");
 	opt_register_early_noarg("--regtest",
 				 opt_set_specific_network, "regtest",
 				 "Alias for --network=regtest");