Add iOS Langfuse analytics via backend events endpoint

AnalyticsService.track() is fire-and-forget — posts to POST /v1/marks/events
which records a Langfuse trace. No external SDK, no Sentry on iOS side.

Events tracked:
- podcast.started (url, cached)
- podcast.completed (url, durationSec) — fires at 97% playback
- podcast.failed (url, error)
- search.semantic (query, resultCount)
- enrich.completed (count)
- collections.generated (collectionCount)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Marks.xcodeproj/project.pbxproj

@@ -8,6 +8,7 @@
 
 /* Begin PBXBuildFile section */
 		0479C0AA16E3AFDBD4414AD0 /* PodcastIndex.swift in Sources */ = {isa = PBXBuildFile; fileRef = F75DE8BE4B3A3E0E60B8BB03 /* PodcastIndex.swift */; };
+		A1B2C3D4E5F60001A2B3C4D5 /* AnalyticsService.swift in Sources */ = {isa = PBXBuildFile; fileRef = A1B2C3D4E5F60002A2B3C4D5 /* AnalyticsService.swift */; };
 		14E1B3CE58D36BFF1A2199C1 /* OnboardingView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 22E006A11D594BFC00A9C4B4 /* OnboardingView.swift */; };
 		15077853ECD40C9B289FB608 /* LinkdingAPI.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5CCBB391B1E0E1E4EBE0EFC7 /* LinkdingAPI.swift */; };
 		41F00F4E7FFC1C0ACF71E398 /* MarksApp.swift in Sources */ = {isa = PBXBuildFile; fileRef = D92575C7C710347F226EC74A /* MarksApp.swift */; };
@@ -82,6 +83,7 @@
 		D3A4B1E764CC88A774AF8EA5 /* EditBookmarkView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = EditBookmarkView.swift; sourceTree = "<group>"; };
 		D92575C7C710347F226EC74A /* MarksApp.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MarksApp.swift; sourceTree = "<group>"; };
 		E895C34E4D2A1C4709B25FF1 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist; path = Info.plist; sourceTree = "<group>"; };
+		A1B2C3D4E5F60002A2B3C4D5 /* AnalyticsService.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AnalyticsService.swift; sourceTree = "<group>"; };
 		F75DE8BE4B3A3E0E60B8BB03 /* PodcastIndex.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PodcastIndex.swift; sourceTree = "<group>"; };
 		F78AA3450BDFAC24591EE407 /* MarksAuth.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MarksAuth.swift; sourceTree = "<group>"; };
 		FE19F7619214271A8C12EEEB /* CollectionsView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CollectionsView.swift; sourceTree = "<group>"; };
@@ -125,6 +127,7 @@
 		7ABBFDF43A1EB773E0A49CFE /* Services */ = {
 			isa = PBXGroup;
 			children = (
+				A1B2C3D4E5F60002A2B3C4D5 /* AnalyticsService.swift */,
 			69D868AF1DAF3F1BBEACBFF6 /* ClaudeService.swift */,
 				5CCBB391B1E0E1E4EBE0EFC7 /* LinkdingAPI.swift */,
 				F78AA3450BDFAC24591EE407 /* MarksAuth.swift */,
@@ -279,6 +282,7 @@
 				A8B8D58C5B68F54DC20126C1 /* BookmarksView.swift in Sources */,
 				5D86F3F0F603B248776916C7 /* BookmarksViewModel.swift in Sources */,
 				706CCE40744D7F382AFFE429 /* BrowserView.swift in Sources */,
+				A1B2C3D4E5F60001A2B3C4D5 /* AnalyticsService.swift in Sources */,
 			BD2EAD8200FB69B95972146F /* ClaudeService.swift in Sources */,
 				6BF0E1F0F4DEAF87B0B8DCF6 /* CollectionsView.swift in Sources */,
 				C3189071834E0F8898408C37 /* EditBookmarkView.swift in Sources */,

Marks/Services/AnalyticsService.swift

@@ -0,0 +1,26 @@
+import Foundation
+
+enum Analytics {
+    static func track(_ event: String, _ properties: [String: Any] = [:]) {
+        Task.detached {
+            do {
+                let token = try await MarksAuth.validToken()
+                guard let url = URL(string: MarksAuth.baseURL + "/v1/marks/events") else { return }
+                var request = URLRequest(url: url)
+                request.httpMethod = "POST"
+                request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
+                request.setValue("application/json", forHTTPHeaderField: "Content-Type")
+                var body: [String: Any] = ["event": event]
+                if !properties.isEmpty { body["properties"] = properties }
+                request.httpBody = try JSONSerialization.data(withJSONObject: body)
+                let (_, response) = try await URLSession.shared.data(for: request)
+                let status = (response as? HTTPURLResponse)?.statusCode ?? 0
+                if status < 200 || status > 299 {
+                    print("[Analytics] \(event) → HTTP \(status)")
+                }
+            } catch {
+                print("[Analytics] \(event) failed: \(error.localizedDescription)")
+            }
+        }
+    }
+}

Marks/Views/BookmarksViewModel.swift

@@ -88,6 +88,7 @@ final class BookmarksViewModel {
             restoreAIData(into: &all)
             bookmarks = try await claude.semanticSearch(query: searchQuery, in: all)
             nextPageUrl = nil
+            Analytics.track("search.semantic", ["query": searchQuery, "resultCount": bookmarks.count])
         } catch {
             self.error = error.localizedDescription
         }
@@ -159,6 +160,7 @@ final class BookmarksViewModel {
         do {
             let allResponse = try await api.fetchBookmarks(limit: 200)
             smartCollections = try await claude.generateCollections(from: allResponse.results)
+            Analytics.track("collections.generated", ["collectionCount": smartCollections.count])
         } catch {
             self.error = error.localizedDescription
         }
@@ -180,6 +182,8 @@ final class BookmarksViewModel {
                 break
             }
         }
+        let enriched = toEnrich.count - bookmarks.indices.filter { bookmarks[$0].aiSummary == nil }.count
+        if enriched > 0 { Analytics.track("enrich.completed", ["count": enriched]) }
         enrichmentProgress = 0
     }
 

Marks/Views/PodcastPlayerView.swift

@@ -59,10 +59,12 @@ final class PodcastPlayerViewModel {
 
         let cached = ClaudeService.cachedPodcastURL(for: articleUrl)
         if FileManager.default.fileExists(atPath: cached.path) {
+            Analytics.track("podcast.started", ["url": articleUrl, "cached": true])
             setupPlayer(url: cached, title: "Podcast")
             return
         }
 
+        Analytics.track("podcast.started", ["url": articleUrl, "cached": false])
         phase = .generating(progress: 0, label: "Starting…")
 
         pollingTask = Task {
@@ -81,13 +83,16 @@ final class PodcastPlayerViewModel {
                         return
                     }
                     if job.isFailed {
-                        phase = .failed(job.error ?? "Generation failed")
+                        let errMsg = job.error ?? "Generation failed"
+                        Analytics.track("podcast.failed", ["url": articleUrl, "error": errMsg])
+                        phase = .failed(errMsg)
                         return
                     }
                     try await Task.sleep(for: .seconds(3))
                 }
             } catch is CancellationError {
             } catch {
+                Analytics.track("podcast.failed", ["url": articleUrl, "error": error.localizedDescription])
                 phase = .failed(error.localizedDescription)
             }
         }
@@ -155,8 +160,14 @@ final class PodcastPlayerViewModel {
 
         let interval = CMTime(seconds: 0.5, preferredTimescale: 600)
         timeObserver = p.addPeriodicTimeObserver(forInterval: interval, queue: .main) { [weak self] t in
-            self?.currentTime = t.seconds
-            self?.updateNowPlaying()
+            guard let self else { return }
+            let prev = self.currentTime
+            self.currentTime = t.seconds
+            self.updateNowPlaying()
+            // Track completion when crossing 97%
+            if self.duration > 1 && prev / self.duration < 0.97 && t.seconds / self.duration >= 0.97 {
+                Analytics.track("podcast.completed", ["url": self.currentArticleUrl, "durationSec": Int(self.duration)])
+            }
         }
 
         setupRemoteCommands()