docs: add installation, privacy, changelog, and 0.1.0 release notes

Phase 6 release collateral:
- README: Installation (unsigned-build/SmartScreen note, requirements,
  first-run downloads) and Privacy & local-first sections
- CHANGELOG.md seeded with the 0.1.0 feature set
- docs/release-notes-0.1.0.md draft for the GitHub Release body

Also corrects the CLIP model download size from ~330 MB to ~580 MB (the
actual model.safetensors is 577 MB) across the docs and the onboarding UI.

docs/release-notes-0.1.0.md

@@ -0,0 +1,59 @@
+# Phokus v0.1.0
+
+> Draft for the GitHub Release body. Paste into the release, fill in the
+> checksum, and trim as needed.
+
+**Phokus is a local-first desktop media library for Windows** — point it at
+your image and video folders and it builds a fast, searchable gallery with
+thumbnails, semantic search, visual discovery, AI tagging, and duplicate
+cleanup. Everything is processed on your machine; nothing is uploaded.
+
+This is the **first public release**. Expect rough edges, and please file
+issues.
+
+## Install
+
+1. Download `Phokus_0.1.0_x64-setup.exe` below.
+2. Run it. **Windows SmartScreen will warn** that the publisher is
+   unrecognized — this build is **not code-signed** (cost; signing is on the
+   roadmap). Click **More info → Run anyway** to proceed.
+3. Requires **Windows 10/11**. The installer fetches the WebView2 runtime
+   automatically if needed.
+
+On first launch, Phokus runs a short guided tour and downloads FFmpeg in the
+background (one-time, ~tens of MB). AI tagging (~1.3 GB) is optional; the CLIP
+model for semantic search (~580 MB) downloads automatically the first time
+embeddings run. **All of this stays on your machine.**
+
+## Highlights
+
+- Virtualized gallery for very large libraries; favorites, ratings, filters, sorts
+- Filename, semantic (`/s`), and tag (`/t`) search
+- Similar-image search, Explore clusters + tag cloud, EXIF Timeline
+- Lightbox with zoom/pan and a custom video player
+- Optional on-device AI tagging (WD tagger)
+- Exact-duplicate finder with bulk delete
+- Built-in updater
+
+See the [changelog](https://github.com/JezzWTF/phokus/blob/main/CHANGELOG.md)
+for the full list.
+
+## Privacy
+
+Your media and all derived data (thumbnails, embeddings, tags, ratings) never
+leave your machine. No account, no telemetry, no cloud. The only network
+activity is the one-time tool/model downloads above and update checks against
+this Releases page.
+
+## Known limitations
+
+- **Unsigned installer** — SmartScreen warning as described above.
+- **Windows only** for now.
+- CPU/DirectML inference in the shipped build; very large libraries take time
+  to embed on first index.
+
+## Verify your download (optional)
+
+```
+SHA-256 (Phokus_0.1.0_x64-setup.exe) = <fill in at publish time>
+```