Add guarded Base canary reader

[FlowmemoryAI]

Summary

• adds npm run index:base-canary / read:base-canary for the documented Base mainnet V0 canary deployment
• requires explicit --acknowledge-mainnet-canary, RPC URL, emitting addresses, and bounded block ranges before reading Base mainnet logs
• persists canonical indexer state plus flowmemory.indexer.base_canary_checkpoint.v0 with productionReady: false
• documents the live canary read over blocks 45955500..45955540 with 4 observations, 0 rejects, and 0 duplicates

Verification

• npm test --prefix services/indexer
• npm run index:base-canary --prefix services/indexer -- --acknowledge-mainnet-canary --rpc-url https://mainnet.base.org --address 0x2a7ADd68a1d45C3251E2F92fFe4926124654a97C --address 0x179Df6d52e9DeF5D02704583a2E4E5a9FF427245 --from-block 45955500 --to-block 45955540 --finalized-block 45955540
• npm test
• npm run launch:candidate
• npm run build --prefix apps/dashboard

Closes #75