Refine sign in flow to match designs and iOS flow (#100)

* Fix dark theme

* First attempt at replicating iOS' UI & flows.

* Try to fix Maestro tests

* Add error dialogs and tests

* Remove unused modifiers

* Try to fix detekt issues

* Tidy up maestro login flow a bit

* Add `CompoundColorPalette` with some needed colors

* Fixes to designs

* Fix detekt issues

* More design fixes

* Some other minor design fixes

* Add changelog

* Minor tweaks.

* Remove legacy dark material theme as it's no longer needed.

* Move sliding sync 'learn more' url to constants object

* Remove unused focusManager

* Change how the displayed homeserver works

* Keep user input as homeserver if it's valid

* Remove `CompoundColorPalette`, try to fix issue when toggling dark mode.

* Add `@Stable` to the theme, adjust how it toggles in dark mode

* Remove unused strings

* Update screenshots

* Re-organize components in LoginRootScreen

* Bump min coverage to 55, max to 60

* Always replace the snapshots contents when running `recordPaparazzi`

* Fix dark theme preview of components using content colors

* Add `BackButton` component

* Handle errors with dialogs in a generic way

* Align our Dialog components with the designs, use them were needed

* Use a `MatrixHomeserverDetails` data class instead of just an URL.

* `AuthenticationService.getHomeserverDetails()` now returns a `StateFlow`.

Also, try to fix coverage issues in tests.

build.gradle.kts

@@ -208,11 +208,11 @@ koverMerged {
             name = "Global minimum code coverage."
             target = kotlinx.kover.api.VerificationTarget.ALL
             bound {
-                minValue = 50
+                minValue = 55
                 // Setting a max value, so that if coverage is bigger, it means that we have to change minValue.
                 // For instance if we have minValue = 25 and maxValue = 30, and current code coverage is now 37.32%, update
                 // minValue to 35 and maxValue to 40.
-                maxValue = 55
+                maxValue = 60
                 counter = kotlinx.kover.api.CounterType.INSTRUCTION
                 valueType = kotlinx.kover.api.VerificationValueType.COVERED_PERCENTAGE
             }
@@ -297,3 +297,15 @@ tasks.register("runQualityChecks") {
     }
     dependsOn(":app:knitCheck")
 }
+
+// Make sure to delete old screenshots before recording new ones
+subprojects {
+    val snapshotsDir = File("${project.path}/src/test/snapshots")
+    val removeOldScreenshotsTask = tasks.register("removeOldSnapshots") {
+        onlyIf { snapshotsDir.exists() }
+        doFirst {
+            snapshotsDir.deleteRecursively()
+        }
+    }
+    tasks.findByName("recordPaparazzi")?.dependsOn(removeOldScreenshotsTask)
+}