Upgrade App Service Plan from P0v3 to P1v3

[kahlstrm]

Upgrade shared App Service Plan from P0v3 (1 vCPU, 4GB) to P1v3 (2 vCPU, 8GB).

Cost: +$58/month ($700/year)

Change

In modules/common/main.tf:

-  sku_name = "P0v3"
+  sku_name = "P1v3"

Prerequisites

• Remove deprecated Forum VM and Mattermost #171 - Remove Forum VM (saves $44/month)
• Add Cloudflare proxy for tietokilta.fi #172 - Add Cloudflare (saves ~$12/month)

Budget

Nonprofit grant: $2000/year

• Current: ~$170/month ($2040/year)
• After prereqs + upgrade: ~$167/month ($2004/year)