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-tauri/tauri.conf.json

@@ -0,0 +1,54 @@
+{
+  "$schema": "https://schema.tauri.app/config/2",
+  "productName": "maarcadetweet",
+  "version": "0.1.0",
+  "identifier": "de.eifelcloud.maarcadetweet",
+  "build": {
+    "beforeDevCommand": "npm run dev",
+    "devUrl": "http://localhost:1430",
+    "beforeBuildCommand": "npm run build",
+    "frontendDist": "../dist"
+  },
+  "app": {
+    "withGlobalTauri": false,
+    "windows": [
+      {
+        "label": "main",
+        "title": "maarcadetweet",
+        "width": 1200,
+        "height": 760,
+        "minWidth": 880,
+        "minHeight": 540,
+        "resizable": true,
+        "decorations": false,
+        "transparent": false,
+        "titleBarStyle": "Overlay",
+        "hiddenTitle": true,
+        "backgroundColor": "#0D0D0D"
+      }
+    ],
+    "security": {
+      "csp": "default-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; connect-src 'self' ipc: http://ipc.localhost"
+    }
+  },
+  "plugins": {
+    "updater": {
+      "active": true,
+      "dialog": true,
+      "endpoints": [
+        "https://releases.maarcadetweet.local/{{target}}/{{arch}}/{{current_version}}"
+      ],
+      "pubkey": ""
+    }
+  },
+  "bundle": {
+    "active": true,
+    "targets": "all",
+    "icon": [
+      "icons/32x32.png",
+      "icons/128x128.png",
+      "icons/128x128@2x.png",
+      "icons/icon.png"
+    ]
+  }
+}