[codex] docs(dev): local bootstrap script for backend

[shinzoxD]

Closes #205.

Summary

• Adds scripts/dev-bootstrap.sh as a single local onboarding entrypoint for dependency install, Docker Compose Postgres startup, DB readiness, migrations, schema validation, and seed loading.
• Adds deterministic local-only seed data in scripts/dev-seed.sql without committing real secrets.
• Updates .env.example to match the Compose host database default and placeholder local API key.
• Documents the bootstrap flow and Bash prerequisite in the README.
• Adds a focused .gitattributes rule so shell scripts stay LF, and fixes migration 005's fresh-DB index target so bootstrap migrations do not reference the non-existent credit_lines.wallet_address column.

Validation

• npm ci passes.
• C:\Program Files\Git\bin\bash.exe -n scripts/dev-bootstrap.sh passes.
• npm run dev:bootstrap -- --skip-install --skip-compose --skip-migrate --skip-seed passes with Git Bash on PATH.
• npm run validate:spec passes.
• Full Docker-backed bootstrap was not run locally because docker is not installed or not on PATH in this environment.
• npm run typecheck still fails on existing baseline errors unrelated to this PR, including missing recordRequest, maintenanceModeGuard, dashboardSummaryService, and log symbols.

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[shinzoxD]

CI note: the fork push workflow failed in the existing \
pm run typecheck\ step before exercising the bootstrap flow. The log matches the current baseline failures also seen on #269: missing symbols such as \
ecordRequest\, \maintenanceModeGuard\, \dashboardSummaryService\, and \log\ in unrelated TypeScript files. Branch-specific checks passed locally: \
pm ci\, \�ash -n scripts/dev-bootstrap.sh\, light-mode \
pm run dev:bootstrap -- --skip-install --skip-compose --skip-migrate --skip-seed\, and \
pm run validate:spec\.

[shinzoxD]

Documenting the CI failure for visibility:

The npm run typecheck step fails with 27 pre-existing TypeScript errors that exist identically on main. This PR touches only non-src/**/*.ts files (.env.example, README.md, scripts/dev-bootstrap.sh, migrations/, package.json) — zero source TypeScript files.

The root cause is an incomplete refactor on main: Container.ts is missing dashboardSummaryService/getCreditService getters, app.ts is missing imports (recordRequest, maintenanceModeGuard, maintenanceRouter, metricsRouter), and drawWebhookService.ts is missing a log import.

This PR's own content (bootstrap script, seed SQL, docs) is fine. Would maintainers prefer a separate baseline-fix PR to resolve the typecheck errors, or should this PR be merged as-is since it doesn't affect CI?

[shinzoxD]

The pre-existing TypeScript baseline errors blocking CI have been fixed in #271 (fix/baseline-typescript-errors). Once that merges, this PR's CI should pass cleanly.