fix(postgres): sanitize all non-identifier chars in table names

[localai-bot]

Problem

sanitizeTableName only replaced -, . and with underscores. Any other character in a collection name leaked into the interpolated CREATE TABLE DDL and produced a SQL syntax error.

This surfaced as mudler/LocalAI#10375: LocalAI namespaces per-user collections as {userID}:{name}. Under legacy API-key auth the userID is the literal legacy-api-key, so an agent's collection name becomes legacy-api-key:<agent>. The : was never sanitized, so:

CREATE TABLE documents_legacy_api_key:LiteraryResearch (...)
ERROR: syntax error at or near ":" (SQLSTATE 42601)

Agents with knowledge base / long-term memory enabled could not create their PostgreSQL collection. (UUID-based user IDs happened to work only because hyphens were in the replace set.)

Fix

Switch sanitizeTableName from a hardcoded denylist to an allowlist: map any character that is not [A-Za-z0-9_] to _. This guarantees a legal unquoted PostgreSQL identifier for any collection name (:, /, @, etc.), while preserving the previous handling of -, . and .

The userID prefix is kept intact, so per-user table isolation on a shared database is preserved - this only makes the existing namespacing scheme PostgreSQL-safe.

Tests

Added rag/engine/sanitize_test.go (Ginkgo, internal package, no DB required):

• the #10375 regression case (: separator),
• a sweep asserting any input sanitizes to a valid identifier,
• a backward-compat assertion for the previously-handled characters.

Red → green confirmed; package builds and vets clean.