Integrate libp2p Gossipsub for Network Broadcasting

[Steake]

Part of Epic: #70 - RC1: Network & Consensus Foundation

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Goal: Use libp2p's Gossipsub protocol for block and transaction propagation to make the network production-ready and scalable.

Requirements:

• Enable libp2p Gossipsub feature in network module
• Subscribe and broadcast on block/transaction/consensus topics
• Implement broadcast and message handler logic

Files:

• crates/bitcell-network/src/transport. rs

Acceptance Criteria:

• Blocks and transactions are gossiped via libp2p
• Network decentralization is enabled and scalable

See critical items in [todo_now.md](https://github.com/Steake/BitCell/blob/master/todo_now. md).

[Steake]

@copilot please start work on this issue and open a PR that references #35 in the title and body.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.

[Steake]

[autopilot] @copilot this issue is marked in-progress but no PR referencing #35 exists yet. Please create a draft PR (even if incomplete) so progress is visible.