feat: swap fees immediately and remove executeBlock system transaction post AllegroModerato

[fgimenez]

Closes #1439

Implements immediate fee swaps during transaction execution, replacing the batched end-of-block approach.

• collectFeePreTx now executes swaps immediately via executeFeeSwap and accumulates fees directly
• Removes collectFeePostTx call (no refunds - users pay max fee upfront)
• Skips fee manager executeBlock system transaction
• Adds distributeFees(validator) for validators to claim accumulated fees on-demand
• Pre-hardfork behavior is preserved for backward compatibility

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Project	Deployment	Review	Updated (UTC)
tempo-docs	Ready	Preview, Comment	Dec 15, 2025 10:35pm

[0xKitsune]

Closing with preference for #1537, most of the changes are carried over with small fixes/changes.