feat(config): move the upload-size ceiling under ingestion settings

Why:
- ADR-0017 names the bound INGESTION_MAX_UPLOAD_SIZE_MB; the code had it
  as APP_MAX_UPLOAD_SIZE_MB. Reconciled to match the ADR, grouped with the
  other three ADR-0017 bounds on IngestionSettings.

.env.example

@@ -9,7 +9,6 @@
 
 # Application
 APP_ENV=local
-APP_MAX_UPLOAD_SIZE_MB=25
 APP_READINESS_CHECK_TIMEOUT_SECONDS=2.0
 
 # Logging
@@ -37,6 +36,7 @@ MINIO_BUCKET=chatbot-source-files
 INGESTION_MAX_CONCURRENCY=4
 INGESTION_THREAD_POOL_SIZE=8
 INGESTION_TIMEOUT_SECONDS=120.0
+INGESTION_MAX_UPLOAD_SIZE_MB=25
 INGESTION_MAX_CHUNKS_PER_FILE=5000
 INGESTION_EMBED_BATCH_SIZE=128
 INGESTION_EMBED_CONCURRENCY=4

src/config.py

@@ -38,10 +38,15 @@ class IngestionSettings(BaseSettings):
     max_concurrency: int = 4
     thread_pool_size: int = 8
     timeout_seconds: float = 120.0
+    max_upload_size_mb: int = 25
     max_chunks_per_file: int = 5000
     embed_batch_size: int = 128
     embed_concurrency: int = 4
 
+    @property
+    def max_upload_size_bytes(self) -> int:
+        return self.max_upload_size_mb * 1024 * 1024
+
 
 class ChunkingSettings(BaseSettings):
     """Parsing and chunking parameters (ADR-0018).
@@ -86,7 +91,6 @@ class AppLimitSettings(BaseSettings):
     model_config = SettingsConfigDict(env_prefix="APP_", extra="ignore")
 
     env: str = "local"
-    max_upload_size_mb: int = 25
     readiness_check_timeout_seconds: float = 2.0