feat(notify-bridge): phase 1 - project scaffolding

Set up the Notify Bridge project structure:
- packages/core (notify_bridge_core) with provider, model, notification, template packages
- packages/server (notify_bridge_server) with FastAPI skeleton and health endpoint
- frontend with SvelteKit 2, Svelte 5, Tailwind CSS v4, static adapter
- Root configs: .gitignore, README.md, CLAUDE.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

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+# Project Guidelines
+
+## Development Servers
+
+**IMPORTANT**: When the user requests it OR when backend code changes are made (files in `packages/server/`), you MUST restart the standalone server using this one-liner:
+```bash
+PID=$(netstat -ano 2>/dev/null | grep ':8420.*LISTENING' | awk '{print $5}' | head -1) && [ -n "$PID" ] && taskkill //F //PID $PID 2>/dev/null; sleep 1 && cd packages/server && pip install -e . 2>&1 | tail -1 && cd ../.. && NOTIFY_BRIDGE_DATA_DIR=./test-data NOTIFY_BRIDGE_SECRET_KEY=test-secret-key-minimum-32chars nohup python -m uvicorn notify_bridge_server.main:app --host 0.0.0.0 --port 8420 > /dev/null 2>&1 & sleep 3 && curl -s http://localhost:8420/api/health
+```
+
+**IMPORTANT**: Overlays (modals, dropdowns, pickers) MUST use `position: fixed` with inline styles and `z-index: 9999`. Tailwind CSS v4 `fixed`/`absolute` classes do NOT work reliably inside flex/overflow containers in this project. Always calculate position from `getBoundingClientRect()` for dropdowns, or use `top:0;left:0;right:0;bottom:0` for full-screen backdrops.
+
+**IMPORTANT**: When the user requests it, restart the frontend dev server using this one-liner:
+```bash
+PID=$(netstat -ano 2>/dev/null | grep ':5173.*LISTENING' | awk '{print $5}' | head -1) && [ -n "$PID" ] && taskkill //F //PID $PID 2>/dev/null; sleep 1 && cd frontend && npx vite dev --port 5173 --host > /dev/null 2>&1 & sleep 4 && curl -s -o /dev/null -w "Frontend: %{http_code}" http://localhost:5173/
+```
+
+## Frontend Architecture Notes
+
+- **i18n**: Uses `$state` rune in `.svelte.ts` file. Locale auto-detects from localStorage. `t()` is reactive via `$state`. `setLocale()` updates immediately without page reload.
+- **Svelte 5 runes**: `$state` only works in `.svelte` and `.svelte.ts` files. Regular `.ts` files cannot use runes -- use plain variables instead.
+- **Static adapter**: Frontend uses `@sveltejs/adapter-static` with SPA fallback. API calls proxied via Vite dev server config.
+- **Auth flow**: After login/setup, use `window.location.href = '/'` (hard redirect), NOT `goto('/')`.
+- **Tailwind CSS v4**: Uses `@theme` directive in `app.css` for CSS variables.
+
+## Backend Architecture Notes
+
+- **SQLAlchemy async + aiohttp**: Cannot nest `async with aiohttp.ClientSession()` inside a route that has an active SQLAlchemy async session -- greenlet context breaks. Eagerly load all DB data before entering aiohttp context.
+- **Jinja2 SandboxedEnvironment**: All template rendering MUST use `from jinja2.sandbox import SandboxedEnvironment`.
+- **System-owned entities**: `user_id=0` means system-owned (e.g. default templates).
+- **FastAPI route ordering**: Static path routes MUST be registered BEFORE parameterized routes.
+- **`__pycache__`**: Add to `.gitignore`. Never commit.