feat: declare the module's settings with settingsSchema()

[pierrejochem]

Change

Mirrors pierrejochem/SpeculumSmartMirror#83 on the reference module.

The Speculum admin console used to render every module option as a raw key/value text row, because nothing told it what a module understands. Modules now declare their own options through ModuleFactory.settingsSchema(), and the console renders typed controls from that declaration.

ExampleModuleFactory declares the two keys the module reads:

override fun settingsSchema(): List<SettingSpec> =
    listOf(
        SettingSpec(
            key = "greeting",
            label = "Greeting",
            default = "Hello, Speculum!",
            help = "Headline text shown at the top of the module.",
        ),
        SettingSpec(
            key = "tickStep",
            label = "Tick step",
            type = SettingType.INT,
            default = "1",
            min = 1,
            max = 100,
            help = "How much the refresh counter advances on each refresh.",
        ),
    )

Each default is the fallback ExampleModule itself reads, which is what the console shows as a hint while a key is unset — deliberately not the same as the starting value defaultConfig() ships. The README gains a Module settings section explaining that distinction and listing the available types.

API version

This needs SettingSpec, SettingType and ModuleFactory.settingsSchema(), so mirrorApi moves from 1.2.2 to 1.3.0 in gradle/libs.versions.toml.

That version is not published yet. CI will fail to resolve org.speculum:mirror-api:1.3.0 until a Speculum release tag publishes it to GitHub Packages. If the next release is numbered differently, that one line is the only change needed.

settingsSchema() has a default empty implementation upstream, so declaring nothing stays valid for modules that do not want typed controls — this PR adopts the new SPI because the example module is the reference for how to write one.

Verification

./gradlew build green — compile, ktlint, detekt and tests — against mirror-api:1.3.0 published to the local Maven repository from the companion branch. Re-run after rebasing onto main (Kotlin 2.4.20, Compose 1.12.1, Gradle 9.8.0), all 16 tasks executed from clean.

ExampleModuleFactoryTest goes from 3 tests to 6: the schema covers every key defaultConfig() ships, the declared types/defaults/bounds match the documented ones, and every entry carries a label and help text.