v1.0.1: CI optimization, changelog update

- CI/CD now only rebuilds images when backend/ or frontend/ changes
- Uses dorny/paths-filter to detect which components changed
- README, docs, and asset changes no longer trigger builds
- Updated CHANGELOG with all recent changes
- Bumped version to 1.0.1

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

.github/workflows/docker-build.yml

@@ -3,8 +3,15 @@ name: Build and Push Docker Images
 on:
   push:
     branches: [main]
+    paths:
+      - 'backend/**'
+      - 'frontend/**'
+      - '.github/workflows/docker-build.yml'
   pull_request:
     branches: [main]
+    paths:
+      - 'backend/**'
+      - 'frontend/**'
   workflow_dispatch:
 
 env:
@@ -13,7 +20,29 @@ env:
   FRONTEND_IMAGE: ghcr.io/${{ github.repository_owner }}/priceghost-frontend
 
 jobs:
+  # Detect which paths changed
+  changes:
+    runs-on: ubuntu-latest
+    outputs:
+      backend: ${{ steps.filter.outputs.backend }}
+      frontend: ${{ steps.filter.outputs.frontend }}
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Check for changes
+        uses: dorny/paths-filter@v3
+        id: filter
+        with:
+          filters: |
+            backend:
+              - 'backend/**'
+            frontend:
+              - 'frontend/**'
+
   build-backend:
+    needs: changes
+    if: needs.changes.outputs.backend == 'true' || github.event_name == 'workflow_dispatch'
     runs-on: ubuntu-latest
     permissions:
       contents: read
@@ -55,6 +84,8 @@ jobs:
           cache-to: type=gha,mode=max
 
   build-frontend:
+    needs: changes
+    if: needs.changes.outputs.frontend == 'true' || github.event_name == 'workflow_dispatch'
     runs-on: ubuntu-latest
     permissions:
       contents: read