Update project configuration for Bookhoard organization rename

Phase 1 of Gitea repository migration:
- Rename docker containers: bookmann_db → bookhoard_db, bookmann → bookhoard
- Update database name: bookmann → bookhoard
- Rename environment variables: BOOKMANN_* → BOOKHOARD_*
- Update documentation references to new project name

This prepares the codebase for migration to Bookhoard organization.

docs/CONVERSION_SERVICE.md

@@ -21,14 +21,14 @@ Check media_item_formats table for existing KEPUB
     ↓
 If KEPUB exists and is recent (< 24 hours):
     → Serve pre-converted file
-    → Set X-Bookmann-KEPUB-SHA256 header
+    → Set X-Bookhoard-KEPUB-SHA256 header
     ↓
 If KEPUB doesn't exist or is stale:
     → Convert EPUB→KEPUB on-the-fly
     → Calculate SHA-256 of converted KEPUB
     → Store in media_item_formats (with converted_from_format_id)
     → Serve converted file
-    → Set X-Bookmann-KEPUB-SHA256 header
+    → Set X-Bookhoard-KEPUB-SHA256 header
     ↓
 Device downloads book with hash in response header
     ↓
@@ -43,9 +43,9 @@ Add these to your `.env` file or `system_config` table:
 
 ```bash
 # Conversion service configuration
-BOOKMANN_CONVERSION_CACHE_DIR=/var/bookmann/cache/kepub
-BOOKMANN_CONVERSION_TOOL=/usr/bin/kepubify  # or /usr/bin/ebook-convert
-BOOKMANN_CONVERSION_CACHE_TTL=24h
+BOOKHOARD_CONVERSION_CACHE_DIR=/var/bookhoard/cache/kepub
+BOOKHOARD_CONVERSION_TOOL=/usr/bin/kepubify  # or /usr/bin/ebook-convert
+BOOKHOARD_CONVERSION_CACHE_TTL=24h
 ```
 
 ### Dockerfile Updates
@@ -76,8 +76,8 @@ GET /opds/devices/{deviceId}/download/{bookId}?format=kepub
 **Response Headers:**
 - `Content-Type`: application/vnd.kobo+xml+zip
 - `Content-Disposition`: attachment; filename="book.kepub.epub"
-- `X-Bookmann-UUID`: uuid-123
-- `X-Bookmann-KEPUB-SHA256`: abc123... (KEPUB-specific hash)
+- `X-Bookhoard-UUID`: uuid-123
+- `X-Bookhoard-KEPUB-SHA256`: abc123... (KEPUB-specific hash)
 
 ## Database Schema
 
@@ -143,7 +143,7 @@ The service tries conversion tools in this order:
 ### Cache Invalidation
 
 Converted KEPUB files are cached for 24 hours by default. This TTL is configurable via:
-- Environment variable: `BOOKMANN_CONVERSION_CACHE_TTL`
+- Environment variable: `BOOKHOARD_CONVERSION_CACHE_TTL`
 - Code: `conversionCacheTTL` field in `ConversionService`
 
 ## Testing
@@ -162,7 +162,7 @@ Use the provided Bruno test:
 This test verifies:
 - KEPUB hash header is present
 - Hash is 64 characters (SHA-256 format)
-- Bookmann UUID header is present
+- Bookhoard UUID header is present
 - Content-Type is correct for KEPUB
 
 ## Troubleshooting
@@ -181,7 +181,7 @@ This test verifies:
 **Problem**: Converted files not being cached
 **Solution**:
 1. Verify cache directory exists and is writable
-2. Check `BOOKMANN_CONVERSION_CACHE_DIR` environment variable
+2. Check `BOOKHOARD_CONVERSION_CACHE_DIR` environment variable
 3. Ensure database can create media_item_formats records
 
 ### Hash Mismatches
@@ -189,7 +189,7 @@ This test verifies:
 **Problem**: Progress sync fails after conversion
 **Solution**:
 1. Verify dual hash storage: both EPUB and KEPUB hashes should exist in `media_item_formats`
-2. Check `X-Bookmann-KEPUB-SHA256` header in response
+2. Check `X-Bookhoard-KEPUB-SHA256` header in response
 3. Ensure `converted_from_format_id` links KEPUB to source EPUB
 
 ## Performance Considerations