Build a cross-platform desktop app (Windows, macOS, Linux)

You are a senior desktop application developer. Build a complete cross-platform desktop app with me, phase by phase, with installers for Windows, macOS and Linux.

## The app
- App name and purpose: [APP NAME], [WHAT IT DOES]
- Who uses it: [USERS]
- Main screens or actions: [LIST]
- Framework: [Electron / Tauri / "you choose"] with [React / Vue / Svelte]
- Works offline? [YES/NO]; syncs with a server? [YES/NO]

## Features
1. App shell: window management, native menus, keyboard shortcuts, system tray, remembers window size and position.
2. Local data in SQLite with migrations; backup and restore; export to CSV or PDF.
3. File handling: open, save, drag and drop, recent files, file associations.
4. The main screens listed above, with undo and redo where it makes sense.
5. Settings screen with theme (light, dark, system) and language.
6. Optional account and cloud sync with conflict handling.
7. Auto-update from [GitHub Releases / my server], with release notes shown to the user.
8. Installers: MSI or NSIS for Windows, DMG for macOS (notarised), AppImage and deb for Linux; code signing steps for each.
9. Crash reporting and an in-app "report a problem" form.

## Desktop rules
- Electron: context isolation on, node integration off, a typed preload bridge, Content Security Policy; Tauri: only the commands and permissions needed.
- Start in under 2 seconds on an average laptop; keep memory use low.
- Never write outside the user's app-data folder without asking.

## Quality rules (apply to every phase)
- Security: prepared statements or an ORM for every query, output escaping, CSRF tokens on every form, passwords hashed with bcrypt or Argon2, rate-limited login, role checks on the server for every admin route, file uploads checked by type and size and stored outside the web root or with random names, secrets only in an .env file.
- Validation: validate every input on the server (and also in the browser for speed). Show clear error messages next to the field that is wrong, and keep what the user already typed.
- Performance: pagination on every list, database indexes on every column used for search, filter or join, lazy-loaded and resized images (WebP), caching for pages that rarely change, no N+1 queries.
- Responsive and accessible: mobile first, works from 360px to wide desktop, proper labels on every form field, keyboard navigation, visible focus, colour contrast of at least 4.5:1, alt text on images.
- SEO: clean URLs, a unique title and meta description per page, canonical tags, Open Graph tags, schema.org JSON-LD where it applies, an XML sitemap and robots.txt.
- Code: small functions with clear names, one responsibility per file, comments only where the reason is not obvious, consistent formatting, no dead code.
- Errors: friendly error pages (404, 500), server errors written to a log, never shown to visitors.
- Deliver with: a README (install steps, .env example, how to create the first admin), database migrations and seed data with realistic sample content, and a deployment checklist.

## How to work with me
Do not write code yet. First reply with:
1. A short summary of what you understood, and anything in the brief that is unclear or contradictory (ask me, do not guess).
2. The final tech stack, with a one-line reason for each choice.
3. The folder and file structure.
4. The full database schema: every table, column, type, index and relation.
5. Every page or screen, and every API endpoint (method, path, who can call it, what it returns).
6. The build plan as numbered phases, each one small enough to finish and test on its own.

Wait for me to reply "go". Then build one phase at a time:
- For every file, give the full path and the complete code. Never write "...", "rest of the code stays the same" or TODO.
- After each phase, tell me how to run it, what to click to test it, and what is still missing. Then wait for me to reply "next".
- If you change a file you already gave me, give the whole updated file again.