feat(ebook): add protected phrase extraction library with config-driven tuning

Refactor protected phrase handling from a single module into a
python/ebook_search/protected_phrases package covering extraction,
storage, and runtime matching. Phrase filtering is now data-driven via
bundled TOML files: ignored_phrases, bad_starts, bad_ends, and
most_common_words.

Add phrase-tuning settings to EbookSearchConfig so candidate generation,
scoring, LLM judging, and matching are configurable rather than hardcoded:
token bounds, entity token limit, raw n-gram min count, frequency and
chapter-spread score thresholds, candidate/LLM/target caps, confidence
threshold, nesting defaults, and the phrase hit boost.

python/ebook_search/protected_phrases/ignored_phrases.toml

@@ -0,0 +1,134 @@
+phrases = [
+  "ended up",
+  "had a",
+  "across the",
+  "anyone in",
+  "are you",
+  "around him",
+  "around the",
+  "as much",
+  "as soon",
+  "before the",
+  "behind him",
+  "between the",
+  "did you",
+  "end up",
+  "he asked",
+  "he concluded",
+  "he continued",
+  "he couldn't",
+  "he did",
+  "he didn't",
+  "he felt",
+  "he had",
+  "he hadn't",
+  "he knew",
+  "he noted",
+  "he pointed",
+  "he realized",
+  "he replied",
+  "he said",
+  "he saw",
+  "he tapped",
+  "he told",
+  "he was",
+  "he wasn't",
+  "his body",
+  "his chair",
+  "his feet",
+  "his hands",
+  "his head",
+  "his office",
+  "his own",
+  "his pc",
+  "his power",
+  "his shield",
+  "his sight",
+  "his voice",
+  "his wrist",
+  "how many",
+  "i am",
+  "i don't",
+  "i was",
+  "i wouldn't",
+  "i'm not",
+  "is in",
+  "is not",
+  "is that",
+  "is the",
+  "it had",
+  "it had",
+  "it was",
+  "it wasn't",
+  "it wasn't",
+  "of course",
+  "of force",
+  "of magic",
+  "of marines",
+  "of power",
+  "of those",
+  "old man",
+  "older man",
+  "set up",
+  "she admitted",
+  "she asked",
+  "she had",
+  "she replied",
+  "she said",
+  "she snapped",
+  "she told",
+  "she was",
+  "she'd been",
+  "shook his",
+  "sure he",
+  "tell you",
+  "that had",
+  "that is",
+  "that was",
+  "there are",
+  "there was",
+  "there were",
+  "they are",
+  "they had",
+  "they were",
+  "they weren't",
+  "this is",
+  "this place",
+  "though he",
+  "through his",
+  "through the",
+  "to find",
+  "to keep",
+  "to stay",
+  "to stop",
+  "to tell",
+  "to try",
+  "told her",
+  "told him",
+  "under his",
+  "was a",
+  "was enough",
+  "was going",
+  "was in",
+  "was no",
+  "was not",
+  "was now",
+  "was on",
+  "was one",
+  "was only",
+  "was still",
+  "was that",
+  "was the",
+  "was there",
+  "were in",
+  "what had",
+  "what happened",
+  "what was",
+  "where the",
+  "while i",
+  "you are",
+  "you can't",
+  "you don't",
+  "you need",
+  "you were",
+]