refactor: enhance JWT authentication and CORS configuration

Updated JWT authentication to use configuration values instead of hardcoded secrets, improving security and flexibility. Enhanced CORS policy to conditionally allow origins based on configuration settings, with logging for permissive defaults. Updated README to reflect project renaming and clarify service context.

_docs/02_document/diagrams/flows/flow_health_probe.md

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+# Flow F7 — Health probe
+
+> Trivial flow. Documented for completeness because it is the contract every external orchestrator (Watchtower, docker compose healthcheck, reverse proxy) relies on.
+
+## Description
+
+`GET /health` returns `{ "status": "healthy" }` with no auth. Confirms the process is up and the HTTP pipeline is serving — does NOT confirm DB connectivity, JWT validation works, or any feature endpoint is reachable.
+
+## Preconditions
+
+- HTTP pipeline is serving (i.e., F6 reached `app.Run()`).
+
+## Sequence Diagram
+
+```mermaid
+sequenceDiagram
+    autonumber
+    participant Probe as Watchtower / compose / reverse proxy
+    participant Host as 07_host
+    Probe->>Host: GET /health (no Authorization header)
+    Host-->>Probe: 200 OK + { "status": "healthy" }
+```
+
+## Flowchart
+
+```mermaid
+flowchart LR
+    Start([GET /health]) --> Resp([200 OK + healthy])
+```
+
+## Data Flow
+
+| Step | From | To | Data | Format |
+|------|------|----|------|--------|
+| 1 | Probe | `MapGet("/health")` | (no body, no auth) | HTTP GET |
+| 2 | `MapGet("/health")` | Probe | `{ "status": "healthy" }` | JSON (PascalCase irrelevant — single key) |
+
+## Error Scenarios
+
+| Error | Where | Detection | Recovery |
+|-------|-------|-----------|----------|
+| Process down | TCP layer | Probe gets `ECONNREFUSED` | Orchestrator restarts container |
+| Pipeline not yet at `app.Run()` (mid-startup) | TCP layer | TCP connect succeeds but no response | Probe times out; orchestrator typically retries with backoff |
+
+## Performance Expectations
+
+| Metric | Target | Notes |
+|--------|--------|-------|
+| Latency | <5ms | Pure pipeline execution; no I/O |
+| Throughput | bounded only by ASP.NET Core's request handling | Not load-tested |
+
+## Future improvement (carry-forward, NOT this Epic)
+
+Add a DB ping:
+
+```csharp
+app.MapGet("/health", async (AppDataConnection db) =>
+{
+    await db.ExecuteAsync("SELECT 1");
+    return Results.Ok(new { status = "healthy" });
+});
+```
+
+This would let `flight-gate` and reverse-proxy checks reflect actual readiness rather than process liveness. Today the migrator runs at startup and crashes the process on DB failure (F6), which is a coarse but workable substitute for one-shot bring-up. In a steady-state running device, a transient DB outage AFTER startup would not be caught by `/health` today.