chore: clean up repo organization

- Standardize on bun: remove package-lock.json, add packageManager field,
  gitignore non-bun lockfiles, fix stray npm install in android:build:clean
- Remove stale build logs and empty dirs (src-tauri/plugins, docs/tickets)
- Move android-dev.sh into scripts/
- Consolidate root docs into docs/ (docker/builder under docs/build/);
  move the architecture overview to docs/architecture/README.md
- Extract Requirements Specification from README into docs/requirements.md
  and slim README down to a project intro + docs index
- Fix internal references to the moved files

docs/build/build-builder-image.md

@@ -0,0 +1,156 @@
+# Building and Pushing the JellyTau Builder Image
+
+This document explains how to create and push the pre-built builder Docker image to your registry for use in Gitea Act CI/CD.
+
+## Prerequisites
+
+- Docker installed and running
+- Access to your Docker registry (e.g., `gitea.tourolle.paris`)
+- Docker registry credentials configured (`docker login`)
+
+## Building the Builder Image
+
+### Step 1: Build the Image Locally
+
+```bash
+# From the project root
+docker build -f Dockerfile.builder -t jellytau-builder:latest .
+```
+
+This creates a local image with:
+- All system dependencies
+- Rust with Android targets
+- Android SDK and NDK
+- Node.js and Bun
+- All build tools pre-installed
+
+### Step 2: Tag for Your Registry
+
+Replace `gitea.tourolle.paris/dtourolle` with your actual registry path:
+
+```bash
+docker tag jellytau-builder:latest gitea.tourolle.paris/dtourolle/jellytau-builder:latest
+```
+
+### Step 3: Login to Your Registry
+
+If not already logged in:
+
+```bash
+docker login gitea.tourolle.paris
+```
+
+### Step 4: Push to Registry
+
+```bash
+docker push gitea.tourolle.paris/dtourolle/jellytau-builder:latest
+```
+
+## Complete One-Liner
+
+```bash
+docker build -f Dockerfile.builder -t jellytau-builder:latest . && \
+docker tag jellytau-builder:latest gitea.tourolle.paris/dtourolle/jellytau-builder:latest && \
+docker push gitea.tourolle.paris/dtourolle/jellytau-builder:latest
+```
+
+## Verifying the Build
+
+Check that the image was pushed successfully:
+
+```bash
+# List images in your registry (depends on registry API support)
+docker search gitea.tourolle.paris/dtourolle/jellytau-builder
+
+# Or pull and test locally
+docker pull gitea.tourolle.paris/dtourolle/jellytau-builder:latest
+docker run -it gitea.tourolle.paris/dtourolle/jellytau-builder:latest bun --version
+```
+
+## Using in CI/CD
+
+The workflow at `.gitea/workflows/build-and-test.yml` automatically uses:
+```yaml
+container:
+  image: gitea.tourolle.paris/dtourolle/jellytau-builder:latest
+```
+
+Once pushed, your CI/CD pipeline will use this pre-built image instead of installing everything during the build, saving significant time.
+
+## Updating the Builder Image
+
+When dependencies change (new Rust version, Android SDK update, etc.):
+
+1. Update `Dockerfile.builder` with the new configuration
+2. Rebuild and push with a new tag:
+
+```bash
+docker build -f Dockerfile.builder -t jellytau-builder:v1.2.0 .
+docker tag jellytau-builder:v1.2.0 gitea.tourolle.paris/dtourolle/jellytau-builder:v1.2.0
+docker push gitea.tourolle.paris/dtourolle/jellytau-builder:v1.2.0
+```
+
+3. Update the workflow to use the new tag:
+
+```yaml
+container:
+  image: gitea.tourolle.paris/dtourolle/jellytau-builder:v1.2.0
+```
+
+## Image Contents
+
+The builder image includes:
+
+- **Base OS**: Ubuntu 24.04
+- **Languages**:
+  - Rust (stable) with targets: aarch64-linux-android, armv7-linux-androideabi, x86_64-linux-android
+  - Node.js 20.x
+  - OpenJDK 17 (for Android)
+- **Tools**:
+  - Bun package manager
+  - Android SDK 34
+  - Android NDK 27.0.11902837
+  - Build essentials (gcc, make, etc.)
+  - Git, curl, wget
+  - libssl, libclang development libraries
+- **Pre-configured**:
+  - Rust toolchain components (rustfmt, clippy)
+  - Android SDK/NDK environment variables
+  - All paths optimized for building
+
+## Build Time
+
+First build takes ~15-20 minutes depending on internet speed (downloads Android SDK/NDK).
+Subsequent builds are cached and take seconds.
+
+## Storage
+
+The built image is approximately **4-5 GB**. Ensure your registry has sufficient storage.
+
+## Troubleshooting
+
+### "Image not found" in CI
+- Verify the image name matches exactly in the workflow
+- Check that the image was successfully pushed: `docker push` output should show successful layers
+- Ensure Gitea has access to your registry (check network/firewall)
+
+### Build fails with "command not found"
+- The image may not have finished pushing. Wait a few moments and retry the CI job.
+- Check that all layers were pushed successfully in the push output.
+
+### Registry authentication in CI
+If your registry requires credentials in CI:
+1. Create a deploy token in your registry
+2. Add to Gitea secrets as `REGISTRY_USERNAME` and `REGISTRY_TOKEN`
+3. Use in workflow:
+```yaml
+- name: Login to Registry
+  run: |
+    docker login gitea.tourolle.paris -u ${{ secrets.REGISTRY_USERNAME }} -p ${{ secrets.REGISTRY_TOKEN }}
+```
+
+## References
+
+- [Docker Build Documentation](https://docs.docker.com/build/)
+- [Docker Push Documentation](https://docs.docker.com/engine/reference/commandline/push/)
+- [Dockerfile Reference](https://docs.docker.com/engine/reference/builder/)