docs(release): v0.5.2 release notes with SHA-256 checksums

RELEASE_NOTES_0.5.2.md

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+# WhispAssist v0.5.2
+
+**Privacy-first, Windows-native meeting assistant — everything on-device, nothing leaves unless you say so.**
+
+A small but important bug-fix release. v0.5.2 fixes a startup crash that could stop WhispAssist
+from opening after an upgrade, and makes any future database problem show a clear message instead
+of failing silently. No feature or privacy changes — everything optional stays off-by-default and
+local-first.
+
+One universal installer (**MSI** and **NSIS**) covers every machine: **Vulkan** for all GPUs
+(NVIDIA/AMD/Intel), the Intel **NPU** (OpenVINO), a **DirectML** fallback, and **CPU**.
+
+---
+
+## 🐛 Fixes
+
+### Fixed: app failing to launch after an upgrade
+On some machines, upgrading could leave the app unable to open at all — no window, no message,
+just nothing. The cause was a database-migration mismatch during startup: WhispAssist would hit
+the error while opening its local database (`wa.db`) and, because the failure happened before the
+window existed, the process exited silently and Windows reported only a generic crash.
+
+### Startup database errors now explain themselves
+Instead of that silent exit, a failure to open `wa.db` now shows a **native error dialog** naming
+the problem and pointing at the database location, then exits cleanly. Your recordings and notes
+are never touched — the message tells you exactly what happened and how to recover, rather than
+leaving you with an app that won't start.
+
+---
+
+## 📦 Install
+
+**Requirements:** Windows 10 or 11 (x64). WhispAssist needs **WebView2** (preinstalled on Windows 11;
+the installer fetches it on Windows 10). Importing from a file/URL additionally needs **`ffmpeg`**
+(and **`yt-dlp`** for URLs) on your PATH — install those separately.
+
+1. Download **`WhispAssist_0.5.2_x64_en-US.msi`** (or the NSIS **`WhispAssist_0.5.2_x64-setup.exe`**).
+2. Run it and accept the UAC prompt. If SmartScreen appears, choose **More info → Run anyway**.
+3. Launch **WhispAssist** from the Start menu.
+
+On first run WA picks the best transcription backend (**NPU → NVIDIA → AMD → Intel → CPU**). It runs
+without admin rights, never adds itself to startup, and keeps all data under
+`%LOCALAPPDATA%\WhispAssist`.
+
+## 🔐 Checksums (SHA-256)
+
+```
+b173b6b15590a65e96d3b24d0ad97666b8d1da905169d807ecc1c51df0584d3e  WhispAssist_0.5.2_x64_en-US.msi
+441b2e7ec7c68be39f9d2381af59ab9eadf916d6d23d0c5541d78bdd88c588b2  WhispAssist_0.5.2_x64-setup.exe
+```
+
+Verify after download:
+
+```powershell
+Get-FileHash .\WhispAssist_0.5.2_x64_en-US.msi -Algorithm SHA256
+```
+
+---
+
+## Privacy, unchanged
+Everything optional is **off by default**. With nothing configured, WhispAssist makes **no content
+egress at all**. Recording is opt-in; sync/AI credentials live only in the OS credential store; the
+MCP server is loopback-only and adds no egress. The reachable-host allowlist is derived from your
+settings and enforced in the core.