maarcadetweet: initial commit

AT Protocol PDS + AppView + Tauri Desktop Client, 160-char post limit.

- PDS (Rust + axum + sqlx)
  - Auth: createAccount, createSession, refreshSession
  - Records: createRecord, deleteRecord (race-safe via SELECT FOR UPDATE)
  - Feed: feed.like.create, feed.repost.create
  - Sync: getRepo, getBlocks, getLatestCommit, getRecord (with MST proof), listRepos
  - Identity: resolveHandle
  - MST: spec-conformant (at-mst crate, 27 tests)
  - Repo: signed commits, TID counter (monotonic, 4096 wrap safe)

- AppView (Rust + axum + sqlx)
  - Jetstream consumer (WebSocket, exponential backoff, 38k+ events indexed)
  - REST API: timeline/home (graph-aware), profile, search, post (with thread hydration)
  - Handle-sync worker (did:plc + did:web)
  - JSONB embed storage + thread columns (migration 0003)
  - Like/repost counter cache (migration 0004)

- Tauri 2 + Svelte 5 Desktop Client
  - System tray (Show/Compose/Quit menu)
  - OS notifications (tauri-plugin-notification)
  - Auto-update (tauri-plugin-updater, placeholder endpoint)
  - Window-state (tauri-plugin-window-state)
  - 160-char compose with live counter
  - Image/Link embed rendering
  - LocalStorage-persisted like state
  - Timeline with poll (prepend new posts)
  - Custom TitleBar (transparent, no decorations)
  - Orange/IBM Plex Mono maarcade design

Tests: 231 Rust + 9 vitest = 240 passed.

crates/tauri-app/src/app.css

@@ -0,0 +1,93 @@
+@import "./lib/styles/tokens.css";
+
+@font-face {
+  font-family: "IBMPlexMono";
+  src: url("/fonts/IBMPlexMono-Regular.ttf") format("truetype");
+  font-weight: 400;
+  font-style: normal;
+  font-display: swap;
+}
+@font-face {
+  font-family: "IBMPlexMono";
+  src: url("/fonts/IBMPlexMono-Medium.ttf") format("truetype");
+  font-weight: 500;
+  font-style: normal;
+  font-display: swap;
+}
+@font-face {
+  font-family: "IBMPlexMono";
+  src: url("/fonts/IBMPlexMono-SemiBold.ttf") format("truetype");
+  font-weight: 600;
+  font-style: normal;
+  font-display: swap;
+}
+@font-face {
+  font-family: "IBMPlexMono";
+  src: url("/fonts/IBMPlexMono-Bold.ttf") format("truetype");
+  font-weight: 700;
+  font-style: normal;
+  font-display: swap;
+}
+@font-face {
+  font-family: "NotoSans";
+  src: url("/fonts/NotoSans-VF.ttf") format("truetype-variations"),
+       url("/fonts/NotoSans-VF.ttf") format("truetype");
+  font-weight: 100 900;
+  font-style: normal;
+  font-display: swap;
+}
+
+*, *::before, *::after { box-sizing: border-box; }
+html, body, #app {
+  margin: 0;
+  padding: 0;
+  height: 100%;
+  background: var(--bg);
+  color: var(--text);
+  font-family: var(--font-sans);
+  font-size: var(--fs-100);
+  line-height: var(--lh-body);
+  -webkit-font-smoothing: antialiased;
+  text-rendering: optimizeLegibility;
+  overflow: hidden;
+}
+
+body {
+  background-image:
+    linear-gradient(var(--orange-3) 1px, transparent 1px),
+    linear-gradient(90deg, var(--orange-3) 1px, transparent 1px);
+  background-size: var(--grid-size) var(--grid-size);
+  background-position: center top;
+}
+
+h1, h2, h3, h4 {
+  font-family: var(--font-mono);
+  font-weight: 700;
+  letter-spacing: var(--tracking-tight);
+  line-height: var(--lh-tight);
+  margin: 0;
+}
+p { margin: 0; }
+a { color: inherit; text-decoration: none; }
+img, svg { display: block; max-width: 100%; }
+
+::selection { background: var(--orange); color: var(--bg); }
+
+:focus-visible {
+  outline: 2px solid var(--orange);
+  outline-offset: 3px;
+  border-radius: 2px;
+}
+
+::-webkit-scrollbar { width: 8px; height: 8px; }
+::-webkit-scrollbar-track { background: transparent; }
+::-webkit-scrollbar-thumb { background: var(--line-2); border-radius: 4px; }
+::-webkit-scrollbar-thumb:hover { background: var(--line); }
+
+@media (prefers-reduced-motion: reduce) {
+  *, *::before, *::after {
+    animation-duration: 0.001ms !important;
+    animation-iteration-count: 1 !important;
+    transition-duration: 0.001ms !important;
+  }
+}