improve analytics (#8418)

* [ee] improve analytics: add git sync & AI chat telemetry, HMAC-signed download

- Add ai_chat_usage table to track chat sessions (session_id, provider, model, mode, message_count)
- Add POST /w/{workspace}/workspaces/log_chat endpoint with upsert on session_id
- Frontend fires logAiChat on every sendRequest, using HistoryManager's existing chat ID
- EE stats: add git_sync_usage (sync vs promotion repo count) and ai_chat_usage (30-day aggregates)
- Replace RSA+AES-GCM encrypted telemetry download with plaintext JSON + HMAC-SHA256 signature
- Signature (12 hex chars) included in download filename for verification
- Update instance settings telemetry descriptions for both EE and CE

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: make StatsDownload struct pub to fix private-interfaces error

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* chore: update ee-repo-ref to 878cc2044717e0177228529a50433fe2768e70b5

This commit updates the EE repository reference after PR #464 was merged in windmill-ee-private.

Previous ee-repo-ref: 33eb863b6b881bd54ed69a540e0c65d5fe125024

New ee-repo-ref: 878cc2044717e0177228529a50433fe2768e70b5

Automated by sync-ee-ref workflow.

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: windmill-internal-app[bot] <windmill-internal-app[bot]@users.noreply.github.com>

backend/windmill-api-workspaces/src/workspaces.rs

@@ -157,6 +157,7 @@ pub fn workspaced_service() -> Router {
             "/protection_rules/:rule_name",
             post(update_protection_rule).delete(delete_protection_rule),
         )
+        .route("/log_chat", post(log_ai_chat))
 }
 pub fn global_service() -> Router {
     Router::new()
@@ -5372,3 +5373,28 @@ async fn compare_two_folders(
         exists_in_fork: target_folder.is_some(),
     });
 }
+
+#[derive(Deserialize)]
+struct LogAiChatPayload {
+    session_id: String,
+    provider: String,
+    model: String,
+    mode: String,
+}
+
+async fn log_ai_chat(
+    Extension(db): Extension<DB>,
+    Json(payload): Json<LogAiChatPayload>,
+) -> Result<StatusCode> {
+    sqlx::query!(
+        "INSERT INTO ai_chat_usage (session_id, provider, model, mode) VALUES ($1, $2, $3, $4)
+         ON CONFLICT (session_id) DO UPDATE SET message_count = ai_chat_usage.message_count + 1",
+        &payload.session_id,
+        &payload.provider,
+        &payload.model,
+        &payload.mode
+    )
+    .execute(&db)
+    .await?;
+    Ok(StatusCode::NO_CONTENT)
+}