chore(cleanup): remove temporary development files and organize .gitignore structure

- Remove coordinator_working.py temporary test coordinator API
- Remove fix_gossip*.patch temporary patch files (gossip2, gossip3, gossip4)
- Add header comments to .gitignore documenting project organization completion
- Add Development Environment section with dev/env/, dev/cache/, dev/scripts/ patterns
- Update Development Tests section header and add dev/multi-chain/ patterns
- Add Logs & Runtime section with dev/cache/

fix_gossip.patch

@@ -1,20 +0,0 @@
---- a/apps/blockchain-node/src/aitbc_chain/consensus/poa.py
-+++ b/apps/blockchain-node/src/aitbc_chain/consensus/poa.py
-@@ -171,7 +171,7 @@
-             )
-             
-             # Broadcast the new block
--            gossip_broker.publish(
-+            await gossip_broker.publish(
-                 "blocks",
-                 {
-                     "height": block.height,
-@@ -207,7 +207,7 @@
-             session.commit()
-             
-             # Broadcast genesis block for initial sync
--            gossip_broker.publish(
-+            await gossip_broker.publish(
-                 "blocks",
-                 {
-                     "height": genesis.height,