Tweaks and fixes throughout the project (#27)

This PR contains the work done to do a little bit of housekeeping pass across all packages and the Website service.

To provide further details about the work:
* Refreshed the READMEs and source documentation to match the current code;
* Tagged every test case consistently across the Infrastructure, Localization, Persistence, and Website test targets;
* Removed Website middleware tests now covered by Infrastructure's own suite;
* Conformed the `PrepareDB` method to Sendable;
* Relaxes the production Compose DATABASE_TLS default from require to prefer;
* Added Persistence test verifying the prefer posture falls back to plaintext connections.

Reviewed-on: rock-n-code/loud-amsterdam#27
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Packages/Infrastructure/README.md

@@ -3,7 +3,6 @@ The shared [Hummingbird](https://github.com/hummingbird-project/hummingbird) too
 
 ## Overview
 The package provides, grouped by role:
-
 | Role | Types |
 | --- | --- |
 | Routing | `RouterController`, `RouteCollectionBuilder`, the `addController` extension on `RouterMethods` |
@@ -11,23 +10,36 @@ The package provides, grouped by role:
 | Pages and assets | `Page`, `Asset`, `AssetExtension`, `FingerprintAssets` |
 | Responses | `CachedHTMLResponse`, `LocalizedHTMLCollectionResponse` |
 | Contexts | `LocalizedRequestContext` |
+| Constants | The `HTTPField.Name` header names, `Int.RateLimit` limits, and `String.Security` header values the middlewares default to |
 
 ## Design rules
 The package holds only what every service can reuse; anything a service owns is injected, never referenced:
-
 - **No site-specific content.** No page markup, no asset catalog, no `Bundle.module` lookups. A type that needs a service's content takes it as a parameter: the `bundle:` whose String Catalog names the supported languages (`LocalizationMiddleware`, `LocalizedHTMLCollectionResponse`, `NotFoundMiddleware`), the `document:` closure that builds a page for a locale, and the `metadata` requirement through which a `Page` conformer supplies its icon links and theme colors.
 - **Services fill the gaps once, via extensions.** A service restores its convenient call sites with retroactive extensions — the Website's `Page+Defaults`, `LocalizationMiddleware+Defaults`, and `NotFoundMiddleware+Defaults` are the pattern to follow.
 - **Method structs.** Single-operation types such as `FingerprintAssets` hold their lifetime-fixed configuration in `init` and take only per-call inputs in `callAsFunction`.
 
 ## Layout
 Sources are split by visibility, then by kind, one type per file:
+```
+Sources/
+├── Public/                public API
+│   ├── Builders/          RouteCollectionBuilder
+│   ├── Enumerations/      AssetExtension
+│   ├── Extensions/        addController, plus the default header names and values
+│   ├── Methods/           FingerprintAssets
+│   ├── Middlewares/       the five HTTP middlewares
+│   ├── Protocols/         Asset, LocalizedRequestContext, Page, RouterController
+│   └── Responses/         CachedHTMLResponse, LocalizedHTMLCollectionResponse
+└── Internal/
+    └── Types/             implementation details (FNV1aHash)
+Tests/
+├── Cases/                 the test suites, mirroring the Sources/ layout
+├── Catalogs/              the String Catalog fixture, copied verbatim so it loads on Linux
+└── Utils/                 stubs (StubAsset, StubPage, …) and the suite Tag constants
+```
 
-```
-Sources/Public/<Kind>/     public API (Protocols, Middlewares, Responses, …)
-Sources/Internal/<Kind>/   implementation details (e.g. FNV1aHash)
-Tests/Cases/…              mirrors the source layout
-Tests/Utils/…              stubs and test-only extensions
-```
+## Testing
+Every suite carries a tag naming the kind of API it exercises — `.asset`, `.extension`, `.middleware`, `.protocol`, or `.type`, declared in `Tests/Utils/Extensions/Tag+Constants.swift` — so test plans and result summaries can slice the run by kind. A new suite must adopt the tag matching its subject (or add a tag there if none fits).
 
 ## Requirements
 - Swift 6.3 toolchain (`swift-tools-version:6.3`).