Add OData filtering and multi-source ingest failover

[ALIPHATICHYD]

Implements the scoped work for:

Closes #81
Closes #82

Summary:

• Adds safe OData-style $filter / $select handling with cursor pagination on list endpoints.
• Adds a pluggable indexer source switcher with RPC primary and Horizon fallback.
• Updates route/tests/docs to match the new behavior.

Summary

Related issue

Type of change

• Bug fix
• New feature
• Refactor
• Docs
• Tests
• CI / tooling

Checklist

• I have read CONTRIBUTING.md
• npx tsc --noEmit passes
• npm run build passes
• I added / updated tests where relevant
• I updated docs where relevant

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[Miracle656]

The risky piece in any OData implementation is SQL injection via the filter expression. This one is safe by construction:

• The parser never builds raw SQL. It emits a Prisma where object ({ field: { contains, mode } }, { field: value }, { field: { gt: value } }, { AND: […] }), and Prisma parameterizes every value before sending it to Postgres.
• Field names are double-gated: an identifier regex ^[A-Za-z_][A-Za-z0-9_\.]*$ plus the caller-supplied fields: Record<string, FieldDefinition> allowlist. Anything not in the allowlist throws — no smuggling id; DROP TABLE.
• Values are coerced per FieldDefinition.type: strict integer regex for numbers, new Date() with validity check for dates, escaped-single-quote handling for strings ('O''Brien' → O'Brien).
• OR is explicitly refused (/\bor\b/i rejects upfront) — limits the surface to AND-of-clauses, which keeps both query shape and parser complexity bounded.
• $select validation is the same shape — identifier regex + allowlist. projectRecord even supports derived computed fields cleanly.
• encodeCursor / decodeCursor are base64url-wrapped { id: number } JSON with integer validation; malformed cursors return undefined so the route falls back to the start instead of throwing.

Multi-source ingest

sources/index.ts switcher with RPC primary + Horizon fallback is the right shape. Tests cover both paths and the failover trigger.

Merging. Closes #81, #82.