fix: remove trailing newlines from migrations to prevent SQLITE_MISUSE errors

Python's sqlite3.executescript() has a bug where trailing newlines after
the final semicolon create empty statements. When APSW's log_sqlite() is
enabled (via apswutils, imported by fastmigrate), these cause visible
"API called with NULL prepared statement" errors during interpreter shutdown.

- Strip trailing newlines from all 9 existing migration files
- Update migration template to end with semicolon, no trailing newline
- Document the requirement in CLAUDE.md

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

migrations/0004-interval-projections.sql

@@ -53,4 +53,4 @@ CREATE TABLE animal_attr_intervals (
 -- Index for "which animals had attr=value at time T" queries
 CREATE INDEX idx_aai_attr_time ON animal_attr_intervals(
     attr, value, start_utc, COALESCE(end_utc, 32503680000000)
-);
+);