feat(nadia): Add database index and devlog query helper

Outcome: done
Changed: devplacepy/database/schema.py:45, devplacepy/database/engagement.py:3-5,194-210, devplacepy/database/__init__.py:11,118
Verified by: `python3 -m py_compile` on all three files — passed; `pyflakes` on engagement.py — clean (no warnings)
Findings: Index idx_posts_project_uid added to init_db at devplacepy/database/schema.py:45 (CREATE INDEX IF NOT EXISTS on posts.project_uid)
Findings: get_project_devlog(project_uid: str, before: str | None = None, viewer: dict | None = None) -> tuple[list, str | None] defined at devplacepy/database/engagement.py:194, returns (list of enriched post dicts, next_cursor) using paginate() with project_uid filter, auto-filtered for deleted_at IS NULL, batch helpers get_users_by_uids and get_comment_counts_by_post_uids, and enrich_items() for post enrichment including author, time_ago, my_vote, comment_count
Findings: get_project_devlog exported from devplacepy/database/__init__.py via import (line 11) and __all__ (line 118)
Open: None
Confidence: high - all acceptance criteria met, syntax verified, no warnings introduced

Typosaurus-Run: 45c0aee6df2649ffaa248729bdfd5841
Typosaurus-Node: 17f01a1e325e40ecb73ffe423f78c4a9
Typosaurus-Agent: @nadia
Refs: #135

devplacepy/database/schema.py

@@ -42,6 +42,7 @@ def init_db():
     _index(db, "posts", "idx_posts_created_at", ["created_at"])
     _index(db, "posts", "idx_posts_topic", ["topic"])
     _index(db, "posts", "idx_posts_slug", ["slug"])
+    _index(db, "posts", "idx_posts_project_uid", ["project_uid"])
     if "posts" in tables:
         posts_table = get_table("posts")
         if not posts_table.has_column("tags"):
@@ -1826,3 +1827,4 @@ def _backfill_gamification():
     for user in pending:
         check_milestone_badges(user["uid"])
     logger.info(f"Gamification backfill processed {len(pending)} users")
+