feat: switch from Admin Center database export to BC API v2.0 data extraction

The Admin Center export API requires an Azure Storage SAS URI which
requires an Azure Subscription - defeating the purpose of an independent
backup. Instead, use BC API v2.0 to extract critical business data
(customers, vendors, items, GL entries, invoices, etc.) as JSON files.

- bc-export.ps1: rewritten to use BC API v2.0 endpoints, extracts 23
  entity types per company with OData pagination support
- bc-backup.sh: handles JSON export directory, creates tar.gz archive
  before encrypting and uploading to S3
- bc-backup.conf.template: removed Azure Storage SAS config, added
  optional BC_COMPANY_NAME filter
- decrypt-backup.sh: updated for tar.gz.gpg format, shows extracted
  entity files and metadata after decryption

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bc-backup.conf.template

@@ -29,7 +29,7 @@ AZURE_CLIENT_SECRET=""
 # 1. Go to API permissions > Add a permission
 # 2. Select "Dynamics 365 Business Central"
 # 3. Select "Application permissions"
-# 4. Check "Automation.ReadWrite.All" or "API.ReadWrite.All"
+# 4. Check "API.ReadWrite.All"
 # 5. Click "Grant admin consent" (requires Global Admin)
 
 # ===================================
@@ -40,28 +40,9 @@ AZURE_CLIENT_SECRET=""
 # Find this in BC Admin Center: https://businesscentral.dynamics.com/
 BC_ENVIRONMENT_NAME=""
 
-# BC Admin API version (default: v2.21)
-BC_API_VERSION="v2.21"
-
-# ===================================
-# Azure Storage Configuration
-# ===================================
-# The BC Admin Center API exports the database to your Azure Storage account.
-# You need an Azure Storage account with a SAS URI that has Read, Write, Create, Delete permissions.
-#
-# To create a SAS URI:
-# 1. Go to Azure Portal > Storage Accounts > your account
-# 2. Go to "Shared access signature"
-# 3. Enable: Blob service, Container+Object resource types, Read+Write+Create+Delete permissions
-# 4. Set an appropriate expiry date
-# 5. Copy the generated SAS URL
-
-# Azure Storage Account SAS URI (full URI with SAS token)
-# Example: https://youraccount.blob.core.windows.net?sv=2021-06-08&ss=b&srt=sco&sp=rwdlac&se=...&sig=...
-AZURE_STORAGE_SAS_URI=""
-
-# Azure Storage container name for exports (will be created automatically)
-AZURE_STORAGE_CONTAINER="bc-exports"
+# Optional: Limit export to a specific company name
+# Leave empty to export all companies in the environment
+BC_COMPANY_NAME=""
 
 # ===================================
 # Encryption Configuration
@@ -128,9 +109,6 @@ CLEANUP_LOCAL="true"
 # Advanced Configuration
 # ===================================
 
-# Maximum time to wait for BC export completion (minutes)
-# MAX_EXPORT_WAIT_MINUTES="120"
-
 # Local temporary directory (default: ./temp)
 # WORK_DIR="/var/tmp/bc-backup"