fix(verifier): drain runtime queue jobs

[pureliture]

What

Fixes the runtime verifier queue drain path for DynamoDB-backed queue payloads.

Why

Historical verifier backfill can enqueue DB-backed verifier jobs, but the drain path was blocked by two runtime issues:

• DynamoDB numeric values in finding snapshots could reach verifier prompt construction as non-JSON primitives.
• Code-scan workers could lease job_type="verify" queue entries and return them to pending, competing with verify-drain.

Changes

• Coerce Location.lineEnd during finding deserialization, matching existing lineStart handling.
• Exclude verifier jobs from lease_next_scan_job() so only lease_next_verify_job() consumes them.
• Add regression coverage for DynamoDB Decimal verifier snapshots and scan-worker/verifier queue isolation.

Validation

• Related verifier/storage/worker pytest coverage passed locally.
• Diff whitespace check passed locally.
• Focused ruff checks for syntax/import regressions passed locally.

Closes #101

[gemini-code-assist]

Code Review

This pull request updates Location.from_dict to cast line_end to an integer to support DynamoDB Decimal types, and modifies lease_next_scan_job to filter out 'verify' jobs from the leased candidates, accompanied by relevant unit tests. Feedback on these changes suggests implementing defensive type coercion when parsing line_end to prevent potential crashes on malformed input. Additionally, there is a concern regarding head-of-line blocking and queue starvation, as filtering 'verify' jobs in-memory after querying a bounded candidate window could exhaust the retrieved window and starve standard scan jobs.

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