chore: add GEMINI.md

Author: mfoo

GEMINI.md

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+# Gemini Context: Home Automation & Infrastructure
+
+This `GEMINI.md` provides context for the AI agent interacting with this repository. This project serves as the Infrastructure-as-Code (IaC) and configuration management repository for a home automation setup powered by Kubernetes on Raspberry Pis.
+
+## Project Overview
+
+*   **Goal:** Manage a home Kubernetes cluster and home automation devices.
+*   **Core Technologies:**
+    *   **Orchestration:** [k3s](https://k3s.io/) (Lightweight Kubernetes).
+    *   **GitOps:** [Flux CD](https://fluxcd.io/) automatically syncs the cluster state with this repository.
+    *   **Configuration Management:** [Ansible](https://www.ansible.com/) configures the bare metal Raspberry Pi nodes.
+    *   **Home Automation:** [Home Assistant](https://www.home-assistant.io/) is the central hub.
+    *   **Dependency Management:** [Renovate](https://github.com/renovatebot/renovate) handles dependency updates.
+
+## Architecture
+
+*   **Hardware:**
+    *   **Cluster:** 3x Raspberry Pi 4 (8GB) nodes (`k8s-master-1`, `k8s-worker-1`, `k8s-worker-2`).
+    *   **Network:** UniFi stack (Dream Machine, Switches, APs).
+    *   **Storage:** Synology DS1621+ NAS (NFS provisioner).
+    *   **Other:** Raspberry Pi 3b (Pi-hole), various IoT devices (Philips Hue, Sonoff, etc.).
+*   **Network Layout:**
+    *   `192.168.1.32/28`: Kubernetes cluster.
+    *   `192.168.1.16/28`: Infrastructure.
+    *   See `README.md` for full VLAN details.
+
+## Directory Structure
+
+*   `ansible/`: Ansible playbooks and inventory for provisioning Raspberry Pis.
+    *   `hosts.yml`: Inventory file defining `kubernetes` and `piholes` groups.
+    *   `site.yml`: Main playbook.
+*   `clusters/home-cluster/`: Kubernetes manifests managed by Flux.
+    *   `flux-system/`: Flux configuration (GitRepository, Kustomization).
+    *   `home-assistant/`, `mosquitto/`, `monitoring/`, etc.: Application specific manifests.
+*   `.github/`: GitHub Actions workflows for linting and maintenance.
+
+## Key Workflows
+
+### 1. GitOps Deployment
+Changes to the `clusters/home-cluster` directory are automatically deployed by Flux.
+*   **Source:** `https://github.com/mfoo/home.git` (branch: `main`).
+*   **Sync Path:** `./clusters/home-cluster`.
+*   **Action:** Commit and push changes to `main`. Flux will pick them up within 1 minute (GitRepository interval) to 10 minutes (Kustomization interval).
+
+### 2. Ansible Configuration
+Used for bootstrapping and managing the OS level of the Raspberry Pis.
+*   **Command:**
+    ```bash
+    ansible-playbook -i ansible/hosts.yml ansible/site.yml
+    ```
+*   **Linter:** CI runs `ansible-lint ansible/site.yml`.
+
+### 3. Adding a New Kubernetes Node
+1.  **Provision OS:** Flash generic OS, set hostname, update packages.
+2.  **Kernel Config:** Add `cgroup_memory=1 cgroup_enable=memory` to `/boot/firmware/cmdline.txt`.
+3.  **Ansible:** Add host to `ansible/hosts.yml` and run the playbook.
+4.  **Join Cluster:** Use `k3sup` (requires SSH access).
+    ```bash
+    k3sup join --server-host k8s-master-1 --host <NEW_NODE_HOSTNAME> --user ubuntu
+    ```
+
+## Development Conventions
+
+*   **Secrets:** Managed via [Sealed Secrets](https://github.com/bitnami-labs/sealed-secrets). **Never commit raw secrets.**
+*   **Formatting:**
+    *   Markdown files are linted.
+    *   Ansible playbooks are linted.
+*   **CI/CD:** GitHub Actions run linting checks on push and PR.