Add persistent gas metering, multi-script selection, and setup/CLI improvements

[SandraOrtiz-wq]

Motivation

• Provide durable local tracking of Google Apps Script usage so the relay can detect daily resets and avoid exhausting a single deployment ID.
• Reduce noisy per-request logging and surface compact, actionable gas/quota status to the CLI.
• Make setup idempotent and user-friendly while enabling multi-script and exit-node configuration for higher throughput and flexible relay chains.
• Improve adaptive transport stability by pausing route switching when runtime metrics indicate elevated loss/variance.

Description

• New SQLite-backed gas meter at src/core/gas_meter.py that records per-script_id calls, errors, and bytes_out, supports daily UTC reset, and selects the least-used/healthiest script.
• Integrated gas meter into DomainFronter (src/relay/domain_fronter.py) to persist counts on each recorded execution, log a compact gas summary every 30s, detect daily resets, warn and auto-switch when a script reaches 90% quota, and fall back when all scripts are exhausted.
• Replaced round-robin script selection with a gas-aware selector and updated blacklist logic to cooperate with the new selector in DomainFronter.
• Added GasMeter usage to CLI main.py with --list-scripts and --reset-gas flags to view or reset per-script counters, preserving backward-compatible script_id handling.
• Reworked the interactive setup wizard (setup.py) to accept multiple script IDs, probe provided script endpoints, optionally configure an exit node (VPS/Cloudflare Worker), toggle relay-chain and features, and write an idempotent config.json with a backup.
• Added an adaptive-transport stabilization pause in src/core/adaptive_transport/engine.py that temporarily blocks route switching when runtime metrics indicate high variance/loss.
• Added unit tests: tests/test_gas_meter.py for GasMeter behavior and tests/test_adaptive_loss_pause.py for the adaptive loss-pause logic.

Testing

• Ran PYTHONPATH=src pytest -q tests/test_gas_meter.py tests/test_adaptive_loss_pause.py and all tests passed (2 passed).
• An initial pytest invocation without PYTHONPATH=src failed during collection due to import-path setup, which was resolved by running tests with PYTHONPATH=src as shown above.
• Tests exercise GasMeter.record_call/get_usage/select_best_script and the adaptive engine's loss-pause triggering and behaved as expected.

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Codex Task