Initial build: stash server + browser extension

Server (Express + better-sqlite3 + FTS5, mirroring keep's stack):
/api/capture (upsert-on-url, per PROPOSAL.md's dedup decision),
/api/articles (list/search/mark-read/delete), plus a minimal
server-rendered reading list and reader view at / and /read/:id
(token passed as ?t= there since browser navigation can't set an
Authorization header). Bearer-token auth generated via `npm run
token` — no login flow, matching keep's one-time identity
registration pattern.

Extension (Manifest V3, sideloaded, no store distribution): toolbar
click or context menu "Send to stash" runs @mozilla/readability
(vendored into extension/lib/) against the current page, falling back
to raw rendered HTML when extraction comes back too thin. Options
page for one-time server URL + token entry.

Verified end-to-end with the real extension loaded in a live Chromium
instance (not just unit-tested extraction logic): capture against a
real page, dedup-on-recapture, mark-read, FTS5 search, 401 on missing
auth, and both server-rendered views all confirmed working.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

extension/manifest.json

@@ -0,0 +1,15 @@
+{
+  "manifest_version": 3,
+  "name": "stash",
+  "version": "0.1.0",
+  "description": "Send the current page to your self-hosted stash read-later.",
+  "permissions": ["activeTab", "scripting", "storage", "contextMenus", "notifications"],
+  "host_permissions": ["<all_urls>"],
+  "background": {
+    "service_worker": "background.js"
+  },
+  "action": {
+    "default_title": "Send to stash"
+  },
+  "options_page": "options.html"
+}