docs: record telesrv sync progress

docs/upstream-sync.md

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+# Upstream Sync Log
+
+This file tracks manual syncs from the private `telesrv` workspace into the public
+`gramsrv` repository. Keep it append-only so future syncs can start from the last
+confirmed source checkpoint.
+
+## Current Checkpoint
+
+- Last synced source commit: `07b2497664bd108dec84f6cfe43715540faf2688`
+- Last synced target commit: `6fd690a`
+- Sync date: 2026-06-09
+- Source path used locally: `D:\work\waikuai\telegram\telesrv`
+- Target path used locally: `D:\work\waikuai\telegram\gramsrv-public`
+
+## Sync History
+
+| Date | Source commit | Target commit | Status | Notes |
+|---|---|---|---|---|
+| 2026-06-09 | `488e409a1898e9c739cc0bd24cb9791636dfd6b3` | `23a2b2a` | synced | Restored sticker path placeholders, media in dialogs/history, media forwarding to channels, and channel history pagination fixes. Source README changes were already covered by the public repo's gramsrv README wording, so no README file changed in the target cherry-pick. |
+| 2026-06-09 | `07b2497664bd108dec84f6cfe43715540faf2688` | `6fd690a` | synced | Kept admin/ban participant changes as transient `updateChannelParticipant` pushes instead of durable channel pts events; added memory/Postgres regression coverage. |
+
+## Next Sync
+
+Start the next batch from source commits after `07b2497664bd108dec84f6cfe43715540faf2688`.
+At the time this log was created, newer `telesrv` commits existed after that point and were
+intentionally left out because this batch was scoped to `488e409` and `07b2497`.