feat: add health endpoint at GET /api/health

[perber]

Adds a lightweight health check endpoint that verifies SQLite connectivity, the data directory, and search index status. Returns 200 OK with check details or 503 if degraded. No authentication required. Prometheus dependency removed.

Includes e2e tests for the health endpoint.

[Copilot]

Pull request overview

Adds a lightweight unauthenticated health check endpoint (GET /api/health) to report basic system readiness (SQLite/search, storage directory, and search indexing status) and backs it with a Playwright e2e test.

Changes:

• Register new health routes in the main wiki router and implement /api/health response shape/status codes (200 vs 503).
• Add search status helpers (IsFailed/IsReady) and a SQLiteIndex.Ping() method used by the health check.
• Add e2e coverage for the health endpoint (and a small local e2e runner tweak).

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/wiki/wiki.go	Wires the new health route registrar into the Wiki router construction/registration.
internal/wiki/importer/use_cases.go	Minor import ordering adjustment.
internal/wiki/health/use_cases.go	Implements health checks (sqlite ping, storage dir existence, search indexing status).
internal/wiki/health/routes.go	Exposes GET /api/health and maps health result to HTTP 200/503 JSON response.
internal/wiki/auth/use_cases.go	Formats NewLoginUseCase as a multi-line function body.
internal/search/sqlite_index.go	Adds Ping() on the SQLite search index.
internal/search/indexing_status.go	Adds IsFailed() and IsReady() helpers for indexing state.
e2e/tests/health.spec.ts	Adds Playwright tests validating health endpoint behavior and unauthenticated access.
e2e/run.sh	Adjusts an argument indentation in local e2e startup.

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