feat: Farm-to-Fork Batch Traceability

[Aditya8369]

closes #1886

Key Components Implemented

1. Immutable Farm Lifecycle Ledger (

backend/models/traceability.py
)
FarmLifecycleLog Audit Model:
Implements cryptographic block hash chaining (previous_hash $\rightarrow$ block_hash $\rightarrow$ digital_signature) using SHA-256.
Records granular farm-to-fork activities:
SEED_SOWING: Seed variety, ICAR certification, non-GMO status, bio-priming.
SOIL_HEALTH: pH, Organic Carbon %, NPK balance, NABL lab accreditation.
BIO_FERTILIZER / BIOPESTICIDE: Neemastra, vermicompost, zero chemical residue verification.
IRRIGATION: FAO-56 solar micro-drip telemetry, water conserved vs flood irrigation.
HARVEST: Selective morning hand-harvesting, Brix sugar index, Grade A+ sorting.
LAB_CERTIFICATION: NABL chemical residue clearance ($0.00\text{ ppm}$ residue safe, Heavy metal free).
PACKAGING & COLD_CHAIN: Biodegradable cornstarch packaging and IoT temperature monitoring.
Carbon Accounting: Tracks kg $\text{CO}_2\text{e}$ sequestered/saved per batch ($2.45\text{ kg CO}_2\text{e}/\text{kg}$ produce).
2. Dynamic QR Code Engine & REST Endpoints (

backend/api/v1/traceability.py
&

backend/services/traceability_service.py
)
GET /api/v1/traceability/generate-qr/<batch_id> – Generates high-resolution, printable packaging QR sticker labels (image/png) complete with batch ID, crop name, farm origin, and organic verification badges.
GET /api/v1/traceability/batches/<batch_id> – Public consumer endpoint fetching verified lifecycle logs, farmer profile, carbon metrics, and lab test reports.
GET /api/v1/traceability/verify/<batch_id> – Cryptographic verification endpoint validating the entire SHA-256 block chain from genesis to store dispatch.
POST /api/v1/traceability/log-event – Appends an immutable lifecycle event to an active batch ledger.
POST /api/v1/traceability/create-batch – Initializes a new farm produce batch and generates the genesis block.

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[github-actions]

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[Aditya8369]

@omroy07 closes #1886

[github-actions]

🎉 Congrats @Aditya8369 on getting your PR merged! 🙌
Thanks for the contribution — looking forward to more from you 🚀