refactor(internal-explorer): read bundle and rejected views from audit RPC only

[niran]

Summary

Part of CHAIN-5418: stop reading the base-bundle-history-* S3 buckets from Internal Explorer so they can be deleted.

• Bundle and rejected views read only the audit events RPC (Postgres-backed). The S3 fallback is gone. When audit is not configured for a chain, bundle returns 404 and rejected returns an empty list. When the audit RPC errors, both return 502 instead of quietly falling back.
• S3 block cache dropped. The block route already rebuilds from the execution RPC on every request, so the cache only served block hashes the RPC could not find. Those lookups now 404. This removes the explorer's only S3 write (PutObject).
• Block view no longer fills in bundle id and metering from S3 when audit has no events for a tx.
• Transaction view drops the S3 archive source: the lookup no longer reads transactions/by_hash or bundles/, the response no longer has archive / coverage.archive, and the page no longer shows the Archive badge or archive wording.
• Deletes app/api/internal-explorer/s3.ts, the S3 client/config in config.ts, the TIPS_<CHAIN>_S3_* entries in .env.example, and the @aws-sdk/client-s3 dependency.

After merge, protocols-ui will bump its base/ui pin and remove the ui_tips_s3 IAM policies and TIPS_*_S3_* chart env.

Screenshots

Transaction page (/internal-explorer/txn/[hash], mainnet tx, audit not configured locally): the Archive provenance badge is gone and the copy now says Audit.

Internal Explorer home (unchanged layout, for reference):

Test plan

• npm test: 55 files, 408 tests pass (transaction-lookup tests updated for the audit-only lookup).
• npx eslint app/api/internal-explorer app/internal-explorer: no new findings.
• npm run build:internal succeeds.
• tsc --noEmit has one error, a missing PNG type declaration in app/vibenet/demos/200/BlockRunner.tsx, which this PR does not touch.

Generated with Toshi

type=routine
risk=low
impact=sev5

[cb-heimdall]

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[linear]

CHAIN-5418