[DOC] CLAUDE.md

CLAUDE.md

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+# HikeBuddy
+
+Hiking assistant app: planning, gear, hike support, tracking. Built for expansion — new features will be added over time.
+
+## Tech Stack
+
+- **Java 21**, Spring Boot 4.0.6
+- **Thymeleaf** for server-side rendered UI
+- **Maven** (wrapper via `mvnw`)
+- **Docker** + Docker Compose for deployment
+
+## Project Structure
+
+```
+src/main/java/de/pitfriedrich/hikebuddy/
+  HikebuddyApplication.java          # Entry point
+  calculator/                        # Hike duration feature
+    HikeDurationController.java      # GET/POST /calculator
+    HikeDurationService.java         # Duration formula logic
+    HikeDurationForm.java            # Form binding (altitudeDifference, distance)
+
+src/main/resources/
+  templates/calculator.html          # Thymeleaf template
+  application.yaml
+```
+
+**Convention:** each feature lives in its own sub-package under `de.pitfriedrich.hikebuddy`.
+
+## Build & Run
+
+```bash
+# Run locally
+./mvnw spring-boot:run
+
+# Run tests
+./mvnw test
+
+# Build JAR
+./mvnw package -DskipTests
+
+# Run via Docker Compose (port 8080)
+docker compose up --build
+```
+
+App runs on `http://localhost:8080`. Root `/` redirects to `/calculator`.
+
+## Key Business Logic
+
+### Hike Duration Formula (`HikeDurationService`)
+
+```
+v1 = altitudeDifference (m) / 300
+v2 = distance (km) / 4
+duration (hours) = max(v1, v2) + 0.5 * min(v1, v2)
+totalMinutes = round(duration * 60)  → displayed as hours + minutes
+```
+
+## Adding New Features
+
+1. Create sub-package under `de.pitfriedrich.hikebuddy.<feature>`
+2. Add Controller, Service, Form/DTO classes
+3. Add Thymeleaf template under `src/main/resources/templates/`
+4. Update `SPEC.md` checklist when done