feat(subgraph): introduce mustache templates

[silent-cipher]

Summary

This PR introduces a template-based build system using Mustache templates to streamline subgraph deployment across different networks (mainnet and calibration). The new system centralizes network configuration in a single JSON file and automatically generates network-specific constants and YAML files.

Migration Guide

Before

cp subgraph_mainnet.yaml subgraph.yaml
# Edit utils/index.ts to set constants
graph codegen
graph build

After

# Single command
npm run build:mainnet

Breaking Changes

None - this is an internal build system change that doesn't affect the deployed subgraph functionality.

Related to #89

[Copilot]

Pull request overview

Introduces a Mustache-template-based build pipeline for the subgraph so that network-specific configuration (mainnet vs calibration) is centralized in subgraph/config/network.json, and network-targeted builds can generate the correct subgraph.yaml and constants automatically.

Changes:

• Added Mustache templates + generation scripts to produce subgraph.yaml and src/generated/constants.ts from config/network.json.
• Updated subgraph mappings to consume generated constants (ContractConstants) instead of hardcoded per-network values.
• Removed legacy per-network subgraph YAML files and updated build scripts/docs to use npm run build:<network>.

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
subgraph/utils/index.ts	Re-exports generated ContractConstants and removes hardcoded proving-period constants.
subgraph/src/pdp-verifier.ts	Switches proving-period config to generated ContractConstants.
subgraph/templates/subgraph.template.yaml	Parameterizes network, address, and start block via Mustache.
subgraph/templates/constants.template.ts	New Mustache template for generated contract constants.
subgraph/config/network.json	New centralized per-network configuration source.
subgraph/scripts/utils/config-loader.js	New helper to load/validate selected network config.
subgraph/scripts/generate-constants.js	New generator for src/generated/constants.ts.
subgraph/scripts/generate-config.js	New generator for subgraph.yaml.
subgraph/package.json	Adds generation + network build scripts and mustache dependency.
subgraph/package-lock.json	Updates lockfile for new deps and Graph tooling versions.
subgraph/.gitignore	Ignores generated subgraph.yaml.
subgraph/subgraph_mainnet.yaml	Removed legacy mainnet manifest file.
subgraph/subgraph_testnet.yaml	Removed legacy testnet manifest file.
README.md	Documents the new configuration and build flow.

Files not reviewed (1)

• subgraph/package-lock.json: Language not supported

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[BigLep]

@FilOzone/storswift : can you please review?

@juliangruber : it may be good to look at this since I assume we'll want to do something similar with the filecoin-pay subgraph.