fix: resolve MCP sidecar image failures (issue #40)

Three fixes for broken MCP sidecars:

1. Remove GitHub MCP sidecar entirely - the upstream image
   (ghcr.io/modelcontextprotocol/servers/github) is discontinued.
   GitHub MCP is now accessed via Copilot API instead.

2. Fix Playwright MCP image - changed from non-existent
   microsoft/playwright-mcp to mcr.microsoft.com/playwright/mcp
   (the official Microsoft Container Registry image).

3. Fix pgtuner MCP startup command - changed --transport to --mode
   and added --host 0.0.0.0 to match the current pgtuner_mcp CLI.

Bumps chart version to 0.3.3.

Closes #40

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

chart/values.yaml

@@ -123,21 +123,6 @@ mcp:
           memory: "256Mi"
           cpu: "500m"
 
-    # GitHub API access (DISABLED: archived image)
-    github:
-      enabled: false
-      image:
-        repository: ghcr.io/modelcontextprotocol/servers/github
-        tag: latest
-      port: 8088
-      resources:
-        requests:
-          memory: "64Mi"
-          cpu: "50m"
-        limits:
-          memory: "256Mi"
-          cpu: "500m"
-
     # PostgreSQL performance tuning
     pgtuner:
       enabled: false  # Requires DATABASE_URI in secrets
@@ -157,7 +142,7 @@ mcp:
     playwright:
       enabled: true
       image:
-        repository: microsoft/playwright-mcp
+        repository: mcr.microsoft.com/playwright/mcp
         tag: latest
       port: 8086
       resources: