feat: Migrate Arbiter and Modpack Version Checker to monorepo

WHAT WAS DONE:
- Migrated Arbiter (discord-oauth-arbiter) code to services/arbiter/
- Migrated Modpack Version Checker code to services/modpack-version-checker/
- Created .env.example for Arbiter with all required environment variables
- Moved systemd service file to services/arbiter/deploy/
- Organized directory structure per Gemini monorepo recommendations

WHY:
- Consolidate all service code in one repository
- Prepare for Gemini code review (Panel v1.12 compatibility check)
- Enable service-prefixed Git tagging (arbiter-v2.1.0, modpack-v1.0.0)
- Support npm workspaces for shared dependencies

SERVICES MIGRATED:
1. Arbiter (Discord OAuth bot) - Originally written by Gemini + Claude
   - Full source code from ops-manual docs/implementation/
   - Created comprehensive .env.example
   - Ready for Panel v1.12 compatibility verification

2. Modpack Version Checker (Python CLI tool)
   - Full source code from ops-manual docs/tasks/
   - Written for Panel v1.11, needs Gemini review for v1.12
   - Never had code review before

STILL TODO:
- Whitelist Manager - Pull from Billing VPS (38.68.14.188)
  - Currently deployed and running
  - Needs Panel v1.12 API compatibility fix (Task #86)
  - Requires SSH access to pull code

NEXT STEPS:
- Gemini code review for Panel v1.12 API compatibility
- Create package.json for each service
- Test npm workspaces integration
- Deploy after verification

FILES:
- services/arbiter/ (25 new files, full application)
- services/modpack-version-checker/ (21 new files, full application)

Signed-off-by: The Golden Chronicler <claude@firefrostgaming.com>

services/modpack-version-checker/docs/INSTALLATION.md

@@ -0,0 +1,166 @@
+# Installation Guide
+
+## Requirements
+
+- Python 3.9 or newer
+- pip (comes with Python)
+- A free CurseForge API key
+
+---
+
+## Step 1 — Install Python
+
+Verify Python is installed:
+
+```bash
+python3 --version
+# Should show: Python 3.9.x or newer
+```
+
+If not installed, download from [python.org](https://www.python.org/downloads/).
+
+---
+
+## Step 2 — Install Modpack Version Checker
+
+### Option A: pip (recommended)
+
+```bash
+pip install modpack-version-checker
+```
+
+### Option B: Install with scheduler support
+
+```bash
+pip install "modpack-version-checker[scheduler]"
+```
+
+This adds APScheduler for the `modpack-checker schedule` background daemon command.
+
+### Option C: Install from source
+
+```bash
+git clone https://github.com/firefrostgaming/modpack-version-checker.git
+cd modpack-version-checker
+pip install -e ".[scheduler]"
+```
+
+---
+
+## Step 3 — Get a CurseForge API Key (free)
+
+1. Go to [console.curseforge.com](https://console.curseforge.com)
+2. Log in or create a free account
+3. Click **Create API Key**
+4. Copy the key
+
+---
+
+## Step 4 — Configure
+
+```bash
+modpack-checker config set-key YOUR_API_KEY_HERE
+```
+
+The key is stored in `~/.config/modpack-checker/config.json`.
+
+---
+
+## Step 5 (Optional) — Set Up Discord Notifications
+
+1. In your Discord server, go to **Channel Settings → Integrations → Webhooks**
+2. Click **New Webhook** and copy the URL
+3. Run:
+
+```bash
+modpack-checker config set-webhook https://discord.com/api/webhooks/YOUR_WEBHOOK_URL
+```
+
+A test message will be sent to confirm it works.
+
+---
+
+## Step 6 — Add Your First Modpack
+
+Find your modpack's CurseForge project ID in the URL:
+`https://www.curseforge.com/minecraft/modpacks/all-the-mods-9` → go to the page, the ID is in the sidebar.
+
+```bash
+modpack-checker add 238222    # All The Mods 9
+modpack-checker add 361392    # RLCraft
+```
+
+---
+
+## Step 7 — Check for Updates
+
+```bash
+modpack-checker check
+```
+
+---
+
+## Background Scheduler (Optional)
+
+Run continuous checks automatically:
+
+```bash
+# Check every 6 hours (default)
+modpack-checker schedule
+
+# Check every 12 hours
+modpack-checker schedule --hours 12
+```
+
+To run as a Linux systemd service, create `/etc/systemd/system/modpack-checker.service`:
+
+```ini
+[Unit]
+Description=Modpack Version Checker
+After=network.target
+
+[Service]
+Type=simple
+User=YOUR_USERNAME
+ExecStart=/usr/local/bin/modpack-checker schedule --hours 6
+Restart=on-failure
+
+[Install]
+WantedBy=multi-user.target
+```
+
+Then:
+```bash
+sudo systemctl enable --now modpack-checker
+```
+
+---
+
+## Uninstall
+
+```bash
+pip uninstall modpack-version-checker
+
+# Remove config and database (optional)
+rm -rf ~/.config/modpack-checker/
+```
+
+---
+
+## Troubleshooting
+
+**`modpack-checker: command not found`**
+- Make sure pip's script directory is in your PATH
+- Try: `python3 -m modpack_checker.cli`
+
+**`Invalid API key`**
+- Double-check the key at [console.curseforge.com](https://console.curseforge.com)
+- Ensure there are no extra spaces when setting it
+
+**`Connection failed`**
+- Check your internet connection
+- CurseForge API may be temporarily down; try again in a few minutes
+
+**`Modpack shows Unknown`**
+- Verify the project ID is correct by checking the CurseForge page
+- Some older modpacks have no files listed via the API