feat: build end-to-end integration test infrastructure with Soroban t…

[Richardkingz2019]

…estnet and Playwright

Closes #30

What this PR does

Implements the complete end-to-end integration test infrastructure requested in issue #30, covering all seven gap areas identified:

New files added

Test infrastructure (src/test/integration/)

• estConfig.ts - Full typed config: base URL, Soroban RPC URL, network passphrase, test account secret, contract IDs (meterRegistry, streamManager, billingLedger), tx confirmation timeout, and per-operation gas cost benchmarks (registerMeter, createStream, submitReading, processBilling).
• setupTestEnvironment.ts - isSorobanRpcHealthy() health probe, captureContractSnapshot() / snapshotsAreDifferent() for snapshot testing, deployTestContracts() placeholder wired to CONTRACT_ID_* env vars, and a LIFO cleanup registry (registerCleanup / runTestCleanup).
• TestWallet.ts - Mock wallet class that simulates Freighter/Stellar wallet connect/disconnect, signTransaction with gas tracking, getTotalGasUsed(), getLastTransactionGas(), and reset(). Throws on signTransaction when not connected. Includes static fromTestConfig() factory.

Test data factories (src/test/factories/)

• meterFactory.ts - Typed Meter records (Electric/Water/Gas, Active/ Inactive/Maintenance) with unit-aware reading and consumption values, meterBatch() helper.

eadingFactory.ts - Typed Reading records with txHash, readingTimeSeries() helper that generates an ascending-timestamp series for a given meter.

• streamFactory.ts - Typed Stream records (Real-time/Batch, Streaming/ Paused/Stopped) with uptime percentages, streamBatch() helper.

E2E specs (src/test/integration/specs/)

egisterMeter.spec.ts - 11 tests covering: page heading, subtitle, Export button, all 8 column headers, meter-001/002/003 rows, Active/ Inactive badges, TestWallet gas benchmark, and Soroban RPC snapshot (skipped when RPC unavailable).

• createStream.spec.ts - 11 tests covering: page heading, subtitle, Export button, all 7 column headers, stream-001/002/003 rows, Streaming/Paused badges, uptime display, TestWallet gas + disconnect error + reset, and Soroban RPC snapshot.
• submitReading.spec.ts - 14 tests covering: Dashboard heading, subtitle, Export button, all 6 summary cards (Active Meters, Total Consumption, Active Streams, Pending Bills, Gas Buffer, Monthly Spend), numeric values, trend indicators, readingFactory unit tests, readingTimeSeries ordering, gas benchmark, and Soroban RPC snapshot.
• �illingFlow.spec.ts - 14 tests covering: Billing heading, subtitle, Export button, View Invoice toggle (show/hide), all 8 column headers, INV-2024-001/002/003 rows, Paid/Pending/Overdue badges, multi-tx gas tracking, wallet transaction history, and Soroban RPC snapshot.

Playwright config (playwright.integration.config.ts)

• testDir points to specs/, 90s test timeout, 15s expect timeout, chromium only, webServer auto-starts Next.js dev server, trace on failure, output to test-results/playwright-integration/.

Docker test environment (docker-compose.test.yml)

• stellar/quickstart:testing with --local --enable-stellar-rpc, health-checked on port 8000/rpc.

CI workflow (.github/workflows/integration.yml)

• Triggers on pull_request to main and workflow_dispatch.
• Spins up stellar service container, installs deps, installs Playwright chromium, runs npm run test:integration with correct env vars.

Supporting changes

• package.json - Added @playwright/test ^1.52.0 devDependency and test:integration script.
• .gitignore - Added /test-results and /playwright-report.
• README.md - Added Integration Testing section with docker + npm run commands for local usage (bash and PowerShell).

Verification

• All TypeScript files pass tsc with zero diagnostics (verified via IDE language server).
• All Soroban-dependent test blocks are gated behind isSorobanRpcHealthy() and self-skip when the RPC is unavailable, so the standard CI lint/build job is not affected.
• UI-only tests (heading, table headers, badge text, toggle interactions) run against the live Next.js dev server and assert on real DOM output from the existing page components.
• Gas benchmark assertions use configurable thresholds from testConfig.ts, injectable via environment variables.

closes #30