Add integration with Jellyseerr/Seerr (#558)

## Description
This PR add the ability to integrate with a [Jellyseerr/Seerr
server](https://github.com/seerr-team/seerr).

### Features
- Login to the Seerr server using API Key, Jellyfin credentials, or
local Seerr credentials
    - Separate Seerr logins per user profile
- Search Seerr from the search page
- Discover media from Seerr on the nav drawer `Discover` page
    - Also from movie, series, or person pages
- Seamless integration with existing media, i.e. selecting media found
from Seerr that already exists on the Jellyfin server, will go directly
to the regular media page
- Mostly consistent UI between Jellyfin media & Seerr media
- Submit requests to Seerr
- Cancel submitted requests

### Screenshots

![discover](https://github.com/user-attachments/assets/f830b48f-e2f1-43f4-9680-9c6d4e071765)

### Related issues
Closes #54

## Acknowledgements

The `app/src/main/seerr/seerr-api.yml` file is copied & modified from
https://github.com/seerr-team/seerr/blob/develop/seerr-api.yml. I hope
to try to upstream some of the changes in the future.

app/src/main/java/com/github/damontecres/wholphin/util/LoadingState.kt

@@ -4,6 +4,8 @@ import com.github.damontecres.wholphin.data.model.BaseItem
 
 /**
  * Generic state for loading something from the API
+ *
+ * @see DataLoadingState
  */
 sealed interface LoadingState {
     data object Pending : LoadingState
@@ -68,3 +70,28 @@ sealed interface HomeRowLoadingState {
             listOfNotNull(message, exception?.localizedMessage).joinToString(" - ")
     }
 }
+
+/**
+ * Generic state for loading something from the API
+ *
+ * @see LoadingState
+ */
+sealed interface DataLoadingState<out T> {
+    data object Pending : DataLoadingState<Nothing>
+
+    data object Loading : DataLoadingState<Nothing>
+
+    data class Success<T>(
+        val data: T,
+    ) : DataLoadingState<T>
+
+    data class Error(
+        val message: String? = null,
+        val exception: Throwable? = null,
+    ) : DataLoadingState<Nothing> {
+        constructor(exception: Throwable) : this(null, exception)
+
+        val localizedMessage: String =
+            listOfNotNull(message, exception?.localizedMessage).joinToString(" - ")
+    }
+}

app/src/main/java/com/github/damontecres/wholphin/util/LocalDateSerializer.kt

@@ -0,0 +1,24 @@
+package com.github.damontecres.wholphin.util
+
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.builtins.serializer
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import java.time.LocalDate
+import java.time.format.DateTimeFormatter
+
+object LocalDateSerializer : KSerializer<LocalDate> {
+    override val descriptor: SerialDescriptor
+        get() = SerialDescriptor("LocalDate", String.serializer().descriptor)
+
+    override fun serialize(
+        encoder: Encoder,
+        value: LocalDate,
+    ) {
+        encoder.encodeString(DateTimeFormatter.ISO_LOCAL_DATE.format(value))
+    }
+
+    override fun deserialize(decoder: Decoder): LocalDate =
+        decoder.decodeString().let { LocalDate.parse(it, DateTimeFormatter.ISO_LOCAL_DATE) }
+}