feat: optimize Docker build context with targeted .dockerignore files

- Add build-specific .dockerignore files to reduce context size
- packages/db: exclude all frontend assets (300MB+ savings)
- packages/api: exclude frontend public assets, keep backend needs
- packages/web: keep public assets, exclude only browser extensions
- Root: exclude browser extensions (400MB+ savings) as fallback

This reduces Docker build context from ~336MB to much smaller sizes
improving build times significantly.

.dockerignore

@@ -8,3 +8,7 @@
 .secrets*.yaml
 apple
 android
+
+# Browser extension builds (large and not needed for server builds)
+pkg/extension
+pkg/extension-v3

packages/api/.dockerignore

@@ -6,3 +6,13 @@ Dockerfile
 .dockerignore
 *.yaml
 .secrets*.yaml
+
+# Exclude large frontend assets not needed for API
+../../packages/web/public/pspdfkit-lib
+../../packages/web/public/static
+../../packages/web/public/pdfjs-dist
+../../packages/web/public/*.mjs
+../../pkg/extension
+../../pkg/extension-v3
+../../apple
+../../android

packages/db/.dockerignore

@@ -2,3 +2,11 @@ node_modules
 .env*
 Dockerfile
 .dockerignore
+
+# Exclude large assets not needed for DB migrations
+../../packages/web/public/pspdfkit-lib
+../../packages/web/public/static
+../../pkg/extension
+../../pkg/extension-v3
+../../apple
+../../android

packages/web/.dockerignore

@@ -7,3 +7,9 @@ Dockerfile
 *.yaml
 .secrets*.yaml
 
+# Web build needs its public assets, but exclude browser extensions
+../../pkg/extension
+../../pkg/extension-v3
+../../apple
+../../android
+