fix(ci): trigger workflow on main branch to enable :latest tag

Changes:
- Create Gitea workflow for ai-stack-deployer
- Trigger on main branch (default branch)
- Use oussamadouhou + REGISTRY_TOKEN for authentication
- Build from ./Dockerfile

This enables :latest tag creation via {{is_default_branch}}.

Tags created:
- git.app.flexinit.nl/oussamadouhou/ai-stack-deployer:latest
- git.app.flexinit.nl/oussamadouhou/ai-stack-deployer:<sha>

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,27 @@
+# Server Configuration
+PORT=3000
+HOST=0.0.0.0
+
+# Hetzner Cloud API (DNS Management)
+# Get token from: https://console.hetzner.cloud/ -> API Tokens
+# Or from BWS: bws-wrapper get <hetzner-token-id>
+HETZNER_API_TOKEN=
+
+# Hetzner DNS Zone ID for flexinit.nl
+HETZNER_ZONE_ID=343733
+
+# Dokploy API
+# Internal URL (only accessible from within infrastructure)
+DOKPLOY_URL=http://10.100.0.20:3000
+# BWS ID: 6b3618fc-ba02-49bc-bdc8-b3c9004087bc
+DOKPLOY_API_TOKEN=
+
+# Stack Configuration
+STACK_DOMAIN_SUFFIX=ai.flexinit.nl
+STACK_IMAGE=git.app.flexinit.nl/oussamadouhou/oh-my-opencode-free:latest
+
+# Traefik Public IP (where DNS records should point)
+TRAEFIK_IP=144.76.116.169
+
+# Reserved names (comma-separated, these cannot be used)
+RESERVED_NAMES=admin,api,www,root,system,test,demo,portal