fix(telemetry): stitch PostHog identities on MemoryClient init

The Python sync/async MemoryClient and the TS MemoryClient were silently
switching their PostHog distinct_id from an anonymous on-disk UUID to the
user's email post-ping, without sending the merge instruction. PostHog
ended up tracking each user as 2-3 disconnected personas (OSS UUID, CLI
anon UUID, email), and only ~4 $create_alias events fired across ~300K
users. The Python CLI does this correctly today; this change ports the
same pattern to MemoryClient.

- mem0/memory/setup.py: make setup_config() idempotent so it backfills a
  top-level user_id for CLI-first users (the CLI writes
  telemetry.anonymous_id, not user_id, which left OSS telemetry silently
  dropped). Add read_anon_ids() and mark_aliased() helpers.
- mem0/memory/telemetry.py: add AnonymousTelemetry.capture_identify() that
  posts a PostHog $identify event with $anon_distinct_id. Add "$identify"
  to _LIFECYCLE_EVENTS so it bypasses the 90% sampling drop.
- mem0/client/main.py: at the end of __init__ for both MemoryClient and
  AsyncMemoryClient, fire $identify for each unaliased anon ID and
  persist telemetry.aliased_to so the alias only happens once per
  (anon_id, email) pair, ever. All telemetry calls swallow exceptions.
- mem0-ts/src/client/telemetry.ts: mirror with captureIdentify().
- mem0-ts/src/client/config.ts (new): node-only readMem0AnonIds() and
  markMem0Aliased() using async dynamic imports of fs/path/os, gated on
  process.versions.node so browsers no-op cleanly.
- mem0-ts/src/client/mem0.ts: call _maybeAliasAnonToEmail() inside
  _initializeClient after ping resolves the email.

Tests cover the matrix (OSS-only, CLI-only, both, already-aliased) plus
failure modes (malformed JSON, read-only fs, posthog errors, browser
env). Telemetry never raises.

mem0-ts/src/client/telemetry.ts

@@ -67,6 +67,15 @@ class UnifiedTelemetry implements TelemetryClient {
     }
   }
 
+  async captureIdentify(anonId: string, email: string) {
+    if (!MEM0_TELEMETRY) return;
+    if (!anonId || !email || anonId === email) return;
+    await this.captureEvent(email, "$identify", {
+      $anon_distinct_id: anonId,
+      client_source: "typescript",
+    });
+  }
+
   async shutdown() {
     // No shutdown needed for direct API calls
   }