chore: add GSD codebase map with 7 analysis documents

Parallel analysis of tech stack, architecture, structure,
conventions, testing patterns, integrations, and concerns.

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

.planning/codebase/STACK.md

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+# Technology Stack
+
+**Analysis Date:** 2026-03-23
+
+## Languages
+
+**Primary:**
+- Go 1.26 - Backend HTTP server and all API logic (`cmd/diunwebhook/main.go`, `pkg/diunwebhook/diunwebhook.go`)
+- TypeScript ~5.7 - Frontend React SPA (`frontend/src/`)
+
+**Secondary:**
+- SQL (SQLite dialect) - Inline schema DDL and queries in `pkg/diunwebhook/diunwebhook.go`
+
+## Runtime
+
+**Environment:**
+- Go 1.26 (compiled binary, no runtime needed in production)
+- Bun (frontend build toolchain, uses `oven/bun:1-alpine` Docker image)
+- Alpine Linux 3.18 (production container base)
+
+**Package Manager:**
+- Go modules - `go.mod` at project root (module name: `awesomeProject`)
+- Bun - `frontend/bun.lock` present for frontend dependencies
+- Bun - `docs/bun.lock` present for documentation site dependencies
+
+## Frameworks
+
+**Core:**
+- `net/http` (Go stdlib) - HTTP server, routing, and handler registration. No third-party router.
+- React 19 (`^19.0.0`) - Frontend SPA (`frontend/`)
+- Vite 6 (`^6.0.5`) - Frontend dev server and build tool (`frontend/vite.config.ts`)
+
+**UI:**
+- Tailwind CSS 3.4 (`^3.4.17`) - Utility-first CSS (`frontend/tailwind.config.ts`)
+- shadcn/ui - Component library (uses Radix UI primitives, `class-variance-authority`, `clsx`, `tailwind-merge`)
+- Radix UI (`@radix-ui/react-tooltip` `^1.1.6`) - Accessible tooltip primitives
+- dnd-kit (`@dnd-kit/core` `^6.3.1`, `@dnd-kit/utilities` `^3.2.2`) - Drag and drop
+- Lucide React (`^0.469.0`) - Icon library
+- simple-icons (`^16.9.0`) - Brand/service icons
+
+**Documentation:**
+- VitePress (`^1.6.3`) - Static documentation site (`docs/`)
+
+**Testing:**
+- Go stdlib `testing` package with `httptest` for handler tests
+- No frontend test framework detected
+
+**Build/Dev:**
+- Vite 6 (`^6.0.5`) - Frontend bundler (`frontend/vite.config.ts`)
+- TypeScript ~5.7 (`^5.7.2`) - Type checking (`tsc -b` runs before `vite build`)
+- PostCSS 8.4 (`^8.4.49`) with Autoprefixer 10.4 (`^10.4.20`) - CSS processing (`frontend/postcss.config.js`)
+- `@vitejs/plugin-react` (`^4.3.4`) - React Fast Refresh for Vite
+
+## Key Dependencies
+
+**Critical (Go):**
+- `modernc.org/sqlite` v1.46.1 - Pure-Go SQLite driver (no CGO required). Registered as `database/sql` driver named `"sqlite"`.
+- `modernc.org/libc` v1.67.6 - C runtime emulation for pure-Go SQLite
+- `modernc.org/memory` v1.11.0 - Memory allocator for pure-Go SQLite
+
+**Transitive (Go):**
+- `github.com/dustin/go-humanize` v1.0.1 - Human-readable formatting (indirect dep of modernc.org/sqlite)
+- `github.com/google/uuid` v1.6.0 - UUID generation (indirect)
+- `github.com/mattn/go-isatty` v0.0.20 - Terminal detection (indirect)
+- `golang.org/x/sys` v0.37.0 - System calls (indirect)
+- `golang.org/x/exp` v0.0.0-20251023 - Experimental packages (indirect)
+
+**Critical (Frontend):**
+- `react` / `react-dom` `^19.0.0` - UI framework
+- `@dnd-kit/core` `^6.3.1` - Drag-and-drop for tag assignment
+- `tailwindcss` `^3.4.17` - Styling
+
+**Infrastructure:**
+- `class-variance-authority` `^0.7.1` - shadcn/ui component variant management
+- `clsx` `^2.1.1` - Conditional CSS class composition
+- `tailwind-merge` `^2.6.0` - Tailwind class deduplication
+
+## Configuration
+
+**Environment Variables:**
+- `PORT` - HTTP listen port (default: `8080`)
+- `DB_PATH` - SQLite database file path (default: `./diun.db`)
+- `WEBHOOK_SECRET` - Token for webhook authentication (optional; when unset, webhook is open)
+
+**Build Configuration:**
+- `go.mod` - Go module definition (module `awesomeProject`)
+- `frontend/vite.config.ts` - Vite config with `@` path alias to `./src`, dev proxy for `/api` and `/webhook` to `:8080`
+- `frontend/tailwind.config.ts` - Tailwind with shadcn/ui theme tokens (dark mode via `class` strategy)
+- `frontend/postcss.config.js` - PostCSS with Tailwind and Autoprefixer plugins
+- `frontend/tsconfig.json` - Project references to `tsconfig.node.json` and `tsconfig.app.json`
+
+**Frontend Path Alias:**
+- `@` resolves to `frontend/src/` (configured in `frontend/vite.config.ts`)
+
+## Database
+
+**Engine:** SQLite (file-based)
+**Driver:** `modernc.org/sqlite` v1.46.1 (pure Go, CGO_ENABLED=0 compatible)
+**Connection:** Single connection (`db.SetMaxOpenConns(1)`) with `sync.Mutex` guarding writes
+**File:** Configurable via `DB_PATH` env var, default `./diun.db`
+
+## Platform Requirements
+
+**Development:**
+- Go 1.26+
+- Bun (for frontend and docs development)
+- No CGO required (pure-Go SQLite driver)
+
+**Production:**
+- Single static binary + `frontend/dist/` static assets
+- Alpine Linux 3.18 Docker container
+- Persistent volume at `/data/` for SQLite database
+- Port 8080 (configurable via `PORT`)
+
+**CI:**
+- Gitea Actions with custom Docker image `gitea.jeanlucmakiola.de/makiolaj/docker-node-and-go` (contains both Go and Node/Bun toolchains)
+- `GOTOOLCHAIN=local` env var set in CI
+
+---
+
+*Stack analysis: 2026-03-23*