Add Taskfile for unified dev workflow across all components (#6080)

## Add Taskfile for unified dev workflow

### Summary
- Introduces [Taskfile](https://taskfile.dev/) as the single CLI entry
point for all development workflows across backend, frontend, engine,
Docker, and desktop
- ~80 tasks organized into 6 namespaces: `backend:`, `frontend:`,
`engine:`, `docker:`, `desktop:`, plus root-level composites
- All CI workflows migrated to use Task
- Deletes `engine/Makefile` and `scripts/build-tauri-jlink.{sh,bat}` —
replaced by Task equivalents
- Removes redundant npm scripts (`dev`, `build`, `prep`, `lint`, `test`,
`typecheck:all`) from `package.json`
- Smart dependency caching: `sources`/`status`/`generates`
fingerprinting, CI-aware `npm ci` vs `npm install`, `run: once` for
parallel dep deduplication

### What this does NOT do
- Does not replace Gradle, npm, or Docker — Taskfile is a thin
orchestration wrapper
- Does not change application code or behavior

### Install
```
npm install -g @go-task/cli    # or: brew install go-task, winget install Task.Task
```

### Quick start
```
task --list       # discover all tasks
task install      # install all deps
task dev          # start backend + frontend
task dev:all      # also start AI engine
task test         # run all tests
task check        # quick quality gate (local dev)
task check:all    # full CI quality gate
```

### Test plan
- [ ] Install `task` CLI and run `task --list` — verify all tasks
display
- [ ] Run `task install` — verify frontend + engine deps install
- [ ] Run `task dev` — verify backend + frontend start, Ctrl+C exits
cleanly
- [ ] Run `task frontend:check` — verify typecheck + lint + test pass
- [ ] Run `task desktop:dev` — verify jlink builds are cached on second
run
- [ ] Verify CI passes on all workflows

---------

Co-authored-by: James Brunton <[email protected]>

frontend/package.json

@@ -79,58 +79,6 @@
     "web-vitals": "^5.1.0"
   },
   "scripts": {
-    "prep": "tsx scripts/setup-env.ts && npm run generate-icons",
-    "prep:saas": "tsx scripts/setup-env.ts --saas && npm run generate-icons",
-    "prep:desktop": "tsx scripts/setup-env.ts --desktop && npm run generate-icons",
-    "prep:desktop-build": "node scripts/build-provisioner.mjs && npm run prep:desktop",
-    "dev": "npm run prep && vite",
-    "dev:core": "npm run prep && vite --mode core",
-    "dev:proprietary": "npm run prep && vite --mode proprietary",
-    "dev:saas": "npm run prep:saas && vite --mode saas",
-    "dev:desktop": "npm run prep:desktop && vite --mode desktop",
-    "dev:prototypes": "npm run prep && vite --mode prototypes",
-    "fix": "npm run format && npm run lint:fix",
-    "format": "prettier --write .",
-    "format:check": "prettier --check .",
-    "lint": "npm run lint:eslint && npm run lint:cycles",
-    "lint:eslint": "eslint --max-warnings=0",
-    "lint:fix": "eslint --fix",
-    "lint:cycles": "dpdm src --circular --no-warning --no-tree --exit-code circular:1",
-    "build": "npm run prep && vite build",
-    "build:core": "npm run prep && vite build --mode core",
-    "build:proprietary": "npm run prep && vite build --mode proprietary",
-    "build:saas": "npm run prep:saas && vite build --mode saas",
-    "build:desktop": "npm run prep:desktop && vite build --mode desktop",
-    "build:prototypes": "npm run prep && vite build --mode prototypes",
-    "preview": "vite preview",
-    "tauri-dev": "npm run prep:desktop && tauri dev --no-watch",
-    "tauri-build": "npm run prep:desktop-build && tauri build",
-    "_tauri-build-dev": "npm run prep:desktop && tauri build",
-    "tauri-build-dev": "npm run _tauri-build-dev -- --no-bundle",
-    "tauri-build-dev-mac": "npm run _tauri-build-dev -- --bundles app",
-    "tauri-build-dev-windows": "npm run _tauri-build-dev -- --bundles nsis",
-    "tauri-build-dev-linux": "npm run _tauri-build-dev -- --bundles appimage",
-    "tauri-clean": "cd src-tauri && cargo clean && cd .. && rm -rf dist build",
-    "typecheck": "npm run typecheck:proprietary",
-    "typecheck:core": "tsc --noEmit --project src/core/tsconfig.json",
-    "typecheck:proprietary": "tsc --noEmit --project src/proprietary/tsconfig.json",
-    "typecheck:saas": "tsc --noEmit --project src/saas/tsconfig.json",
-    "typecheck:desktop": "tsc --noEmit --project src/desktop/tsconfig.json",
-    "typecheck:prototypes": "tsc --noEmit --project src/prototypes/tsconfig.json",
-    "typecheck:scripts": "tsc --noEmit --project scripts/tsconfig.json",
-    "typecheck:all": "npm run typecheck:core && npm run typecheck:proprietary && npm run typecheck:saas && npm run typecheck:desktop && npm run typecheck:prototypes && npm run typecheck:scripts",
-    "check": "npm run typecheck && npm run lint && npm run test:run",
-    "generate-licenses": "node scripts/generate-licenses.js",
-    "generate-icons": "node scripts/generate-icons.js",
-    "generate-icons:verbose": "node scripts/generate-icons.js --verbose",
-    "generate-sample-pdf": "node scripts/sample-pdf/generate.mjs",
-    "test": "vitest",
-    "test:run": "vitest run",
-    "test:watch": "vitest --watch",
-    "test:coverage": "vitest --coverage",
-    "test:e2e": "playwright test",
-    "test:e2e:ui": "playwright test --ui",
-    "test:e2e:install": "playwright install",
     "update:minor": "npm outdated || npm update --before=$(date -v-7d +%Y-%m-%d) && (npm audit fix --before=$(date -v-7d +%Y-%m-%d) || true) && npm test",
     "update:major": "npx npm-check-updates -u && npm install",
     "update:interactive": "npx npm-check-updates -i",