Move redaction policy validation into the builder via a new
`RedactorBuilder::try_build` constructor that surfaces compile errors
(custom-string regex failures, duplicate session mappings, empty
patterns) instead of silently ignoring them, and release the crate as
v0.5.1. Hardens LLM and restore paths by limiting Ollama response size
and timeout, constraining unterminated token candidates with a shared
`MAX_TOKEN_CANDIDATE_BYTES` cap, and filtering LLM findings to the
provided redactable ranges. Consolidates service-layer redaction
helpers and session prior-validation into dedicated routines.

Signed-off-by: Cloudiful <bunnies-spender.0h@icloud.com>