refactor(backend): clean up jail service, add error handling service

- Extract jail status/processing to helper functions
- Add error_handling.py service for centralized error handling
- Update config.py with validation and defaults
- Update .env.example with all config options
- Remove obsolete Tasks.md, add Service-Development.md
- Minor fixes across routers and services

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/app/config.py

@@ -534,6 +534,35 @@ class Settings(BaseSettings):
         ge=1,
         description="Max config update requests per IP per minute.",
     )
+    # -------------------------------------------------------------------------
+    # Pagination & display limits (configurable per deployment)
+    # -------------------------------------------------------------------------
+    max_page_size: int = Field(
+        default=500,
+        ge=1,
+        le=10000,
+        description=(
+            "Maximum number of records returned per paginated API response. "
+            "Individual endpoints may further limit this value. "
+            "Must be between 1 and 10000."
+        ),
+    )
+    blocklist_preview_max_lines: int = Field(
+        default=100,
+        ge=1,
+        description=(
+            "Maximum number of IP lines returned in a blocklist source preview. "
+            "Must be at least 1."
+        ),
+    )
+    history_retention_days: int = Field(
+        default=90,
+        ge=1,
+        description=(
+            "Number of days historical ban records are retained before being "
+            "archived or purged by the cleanup task. Must be at least 1."
+        ),
+    )
 
     @field_validator("elasticsearch_hosts", mode="before")
     @classmethod