Merge pull request #2 from olujimiAdebakin/feature/campaign

feat(campaign): fix stack-too-deep errors and achieve clean compilation

- Inlined Milestone struct assignment in `createMilestone()` by removing `_storeMilestone()` and writing fields individually to storage – eliminates the >16-slot struct literal that breaks both legacy and IR codegen
- Fixed `getPendingRefunds()` view function – added missing return logic and early-empty return (removes compiler warning)
- Cleaned up `foundry.toml`: removed conflicting `viaIR`/`via_ir` flags, kept only `via_ir = true` with high optimizer runs
- Added proper token address validation in `_validateCampaignParameters()` (now uses the previously ignored `token` param with `extcodesize` check + custom `Factory_InvalidTokenAddress` error)
- Minor clean-ups: removed unused internal helper functions, improved comments

Author: olujimiAdebakin

foundry.toml

@@ -2,7 +2,15 @@
 src = "src"
 out = "out"
 libs = ["lib"]
-viaIR = true
+
+# Correct settings for Foundry ≥ 0.2.0 (2024–2025)
+via_ir = true    
+optimizer = true
+optimizer_runs = 1_000_000
+
+# Optional but recommended
+ffi = false
+fs_permissions = [{ access = "read-write", path = "./"}]
 
 # viaIR: true;