feat: implement topic-based repository discovery and filtering

- Introduce `TopicCategory` with predefined sets of matching topics and search keywords for Privacy, Media, Productivity, Networking, and Dev Tools.
- Add `SwitchTopic` action to `HomeViewModel` to allow filtering the discovery feed by specific categories.
- Implement a topic supplement loading mechanism in `HomeViewModel` that combines standard category results with keyword-based GitHub searches for better discovery.
- Enhance `HomeRepository` and its implementation to support searching repositories by topic keywords with caching.
- Update `HomeRoot` UI to include a horizontally scrollable list of `FilterChip` components for topic selection.
- Implement a scroll-aware header in `HomeRoot` that animates the visibility of the top bar and filter chips based on scroll direction.
- Add localized strings and icons for the new topic categories.
- Refactor repository-to-UI mapping into a reusable `mapReposToUi` function.

Author: rainxchzed

core/presentation/src/commonMain/composeResources/values/strings.xml

@@ -270,6 +270,12 @@
     <string name="home_category_hot_release">Hot release</string>
     <string name="home_category_most_popular">Most popular</string>
 
+    <string name="home_topic_privacy">Privacy</string>
+    <string name="home_topic_media">Media</string>
+    <string name="home_topic_productivity">Productivity</string>
+    <string name="home_topic_networking">Network</string>
+    <string name="home_topic_dev_tools">Dev Tools</string>
+
     <string name="home_finding_repositories">Finding repositories...</string>
     <string name="home_loading_more">Loading more...</string>
     <string name="home_no_more_repositories">No more repositories</string>

feature/home/data/src/commonMain/kotlin/zed/rainxch/home/data/repository/HomeRepositoryImpl.kt

@@ -269,6 +269,39 @@ class HomeRepositoryImpl(
             )
         }.flowOn(Dispatchers.IO)
 
+    override fun searchByTopic(
+        searchKeywords: String,
+        platform: DiscoveryPlatform,
+        page: Int,
+    ): Flow<PaginatedDiscoveryRepositories> =
+        flow {
+            val cacheCategory = "topic_${searchKeywords.hashCode()}"
+            val localCached =
+                cacheManager.get<PaginatedDiscoveryRepositories>(
+                    cacheKey(
+                        category = cacheCategory,
+                        requestedPlatform = platform,
+                        page = page,
+                    ),
+                )
+            if (localCached != null && localCached.repos.isNotEmpty()) {
+                logger.debug("Using cached topic repos: ${localCached.repos.size}")
+                emit(localCached)
+                return@flow
+            }
+
+            emitAll(
+                searchReposWithInstallersFlow(
+                    platform = platform,
+                    baseQuery = "$searchKeywords in:name,description,topics stars:>10 archived:false",
+                    sort = "stars",
+                    order = "desc",
+                    startPage = page,
+                    category = cacheCategory,
+                ),
+            )
+        }.flowOn(Dispatchers.IO)
+
     private fun searchReposWithInstallersFlow(
         platform: DiscoveryPlatform,
         baseQuery: String,

feature/home/domain/src/commonMain/kotlin/zed/rainxch/home/domain/model/TopicCategory.kt

@@ -0,0 +1,64 @@
+package zed.rainxch.home.domain.model
+
+enum class TopicCategory(
+    val matchTopics: Set<String>,
+    val searchKeywords: String,
+) {
+    PRIVACY(
+        matchTopics = setOf(
+            "privacy", "security", "encryption", "vpn", "firewall",
+            "password-manager", "privacy-tools", "e2ee", "secure",
+            "anonymity", "tor", "pgp", "2fa", "auth",
+        ),
+        searchKeywords = "privacy security encryption vpn firewall",
+    ),
+    MEDIA(
+        matchTopics = setOf(
+            "music-player", "video-player", "media", "podcast", "streaming",
+            "audio", "video", "media-player", "music", "player",
+            "mpv", "vlc", "recorder", "screen-recorder", "gallery",
+        ),
+        searchKeywords = "music-player video-player media podcast audio",
+    ),
+    PRODUCTIVITY(
+        matchTopics = setOf(
+            "productivity", "file-manager", "notes", "launcher", "keyboard",
+            "browser", "calendar", "todo", "note-taking", "editor",
+            "organizer", "task-manager", "markdown", "writing",
+        ),
+        searchKeywords = "productivity file-manager notes launcher browser",
+    ),
+    NETWORKING(
+        matchTopics = setOf(
+            "proxy", "dns", "ad-blocker", "torrent", "downloader",
+            "network", "ssh", "wireguard", "adblock", "download-manager",
+            "firewall", "socks5", "http-proxy", "p2p", "ftp",
+        ),
+        searchKeywords = "proxy dns ad-blocker torrent downloader network",
+    ),
+    DEV_TOOLS(
+        matchTopics = setOf(
+            "terminal", "developer-tools", "git-client", "editor", "cli",
+            "ide", "devtools", "code-editor", "terminal-emulator", "development",
+            "adb", "debugger", "api-client", "shell", "sdk",
+        ),
+        searchKeywords = "terminal developer-tools git-client code-editor cli",
+    ),
+    ;
+
+    fun matchesRepo(
+        topics: List<String>?,
+        description: String?,
+        name: String?,
+    ): Boolean {
+        val repoTopics = topics?.map { it.lowercase() }.orEmpty()
+        if (repoTopics.any { it in matchTopics }) return true
+
+        val desc = description?.lowercase() ?: ""
+        val repoName = name?.lowercase() ?: ""
+        val keywords = searchKeywords.split(" ")
+        return keywords.any { keyword ->
+            desc.contains(keyword) || repoName.contains(keyword)
+        }
+    }
+}

feature/home/domain/src/commonMain/kotlin/zed/rainxch/home/domain/repository/HomeRepository.kt

@@ -19,4 +19,10 @@ interface HomeRepository {
         platform: DiscoveryPlatform,
         page: Int,
     ): Flow<PaginatedDiscoveryRepositories>
+
+    fun searchByTopic(
+        searchKeywords: String,
+        platform: DiscoveryPlatform,
+        page: Int,
+    ): Flow<PaginatedDiscoveryRepositories>
 }

feature/home/presentation/src/commonMain/kotlin/zed/rainxch/home/presentation/HomeAction.kt

@@ -3,6 +3,7 @@ package zed.rainxch.home.presentation
 import zed.rainxch.core.domain.model.DiscoveryPlatform
 import zed.rainxch.core.presentation.model.GithubRepoSummaryUi
 import zed.rainxch.home.domain.model.HomeCategory
+import zed.rainxch.home.domain.model.TopicCategory
 
 sealed interface HomeAction {
     data object Refresh : HomeAction
@@ -27,6 +28,10 @@ sealed interface HomeAction {
         val category: HomeCategory,
     ) : HomeAction
 
+    data class SwitchTopic(
+        val topic: TopicCategory?,
+    ) : HomeAction
+
     data class SwitchFilterPlatform(
         val platform: DiscoveryPlatform,
     ) : HomeAction