fix: trigger CI on master (repo default branch), drop unsupported Python matrix entries

Workflows listened on 'main'/'develop' but the repo's default branch is
master, so push events never started a job (every historical run is a
schedule event). Point push/PR triggers and the deploy-gate refs at
master, and trim the test matrix to 3.11/3.12 to match
requires-python >=3.11.

.gitea/workflows/ci.yml

@@ -2,9 +2,9 @@ name: CI/CD Pipeline - Northern Thailand Ping River Monitor
 
 on:
   push:
-    branches: [ main, develop ]
+    branches: [ master, develop ]
   pull_request:
-    branches: [ main ]
+    branches: [ master ]
   schedule:
     # Run tests daily at 2 AM UTC
     - cron: '0 2 * * *'
@@ -23,7 +23,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.11', '3.12']
     
     steps:
     - name: Checkout code
@@ -271,7 +271,7 @@ jobs:
     name: Deploy to Production
     runs-on: ubuntu-latest
     needs: [test, build, integration-test]
-    if: github.ref == 'refs/heads/main'
+    if: github.ref == 'refs/heads/master'
     environment:
       name: production
       url: https://ping-river-monitor.b4l.co.th
@@ -303,7 +303,7 @@ jobs:
     name: Performance Test
     runs-on: ubuntu-latest
     needs: deploy-production
-    if: github.ref == 'refs/heads/main'
+    if: github.ref == 'refs/heads/master'
     
     steps:
     - name: Checkout code