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.

CHANGELOG.md

@@ -0,0 +1,48 @@
+# Changelog
+
+All notable changes to Phokus are documented here. The format is based on
+[Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project
+aims to follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html)
+(0.x: anything may change between minor versions).
+
+## [0.1.0] — Unreleased
+
+First public release. Windows desktop, distributed as an unsigned NSIS
+installer with a built-in updater.
+
+### Added
+
+- **Local media library** — add folders, recursive background indexing with
+  live progress, and a filesystem watcher that keeps the library in sync as
+  files are added, edited, moved, renamed, or removed (thumbnails and
+  embeddings are preserved across renames).
+- **Gallery** — virtualized grid (handles very large libraries), favorites,
+  star ratings, video durations; filter by folder, type, favorites, or
+  rating; sort by date added, date taken (EXIF), name, size, rating, or
+  duration; compact / comfortable / detail density.
+- **Search** — filename, semantic (`/s`, via CLIP visual embeddings), and tag
+  (`/t`) search from one prefix-aware search bar.
+- **Discovery** — similar-image search (by image or selected region), an
+  Explore view with a visual cluster map and tag cloud, and a Timeline grouped
+  by EXIF capture date. Explore, Timeline, and Duplicates are folder-scopable
+  from their headers.
+- **Lightbox** — keyboard navigation, zoom, pan, inline tag editing, and
+  rating controls, plus a custom edge-to-edge video player (scrubbing, volume,
+  speed, loop, fullscreen, keyboard support).
+- **AI tagging** — WD tagger (ONNX, CPU/DirectML) with adjustable confidence
+  threshold, batch size, and per-folder queue targeting. Optional.
+- **Duplicate finder** — three-phase exact-duplicate scan
+  (size → sample hash → full hash) with live progress and bulk delete.
+- **Background pipeline** — strict-priority workers (thumbnails → metadata →
+  embeddings → tags) with per-folder pausing from the sidebar context menu or
+  the background-tasks bar.
+- **Guided first-run onboarding** — background FFmpeg provisioning with live
+  progress and retry, a walkthrough of the library, pipeline, search modes,
+  and views, and an optional AI-tagger download. Re-runnable from Settings.
+- **Updater** — checks GitHub Releases on launch and from Settings; downloads
+  and installs signed update artifacts.
+- **Maintenance** — database compaction and orphaned-thumbnail cleanup from
+  Settings, with live size/reclaimable stats.
+- **Window state** persistence and single-instance handling.
+
+[0.1.0]: https://github.com/JezzWTF/phokus/releases/tag/v0.1.0