Rename content_hash/output_hash to cid throughout

Refactor to use IPFS CID as the primary content identifier:
- Update database schema: content_hash -> cid, output_hash -> output_cid
- Update all services, routers, and tasks to use cid terminology
- Update HTML templates to display CID instead of hash
- Update cache_manager parameter names
- Update README documentation

This completes the transition to CID-only content addressing.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -5,7 +5,7 @@ L1 rendering server for the Art DAG system. Manages distributed rendering jobs v
 ## Features
 
 - **3-Phase Execution**: Analyze → Plan → Execute pipeline for recipe-based rendering
-- **Content-Addressable Caching**: SHA3-256 hashed content with deduplication
+- **Content-Addressable Caching**: IPFS CIDs with deduplication
 - **IPFS Integration**: Optional IPFS-primary mode for distributed storage
 - **Storage Providers**: S3, IPFS, and local storage backends
 - **DAG Visualization**: Interactive graph visualization of execution plans
@@ -130,13 +130,13 @@ Interactive docs: http://localhost:8100/docs
 
 | Method | Path | Description |
 |--------|------|-------------|
-| GET | `/cache/{hash}` | Get cached content (with preview) |
-| GET | `/cache/{hash}/raw` | Download raw content |
-| GET | `/cache/{hash}/mp4` | Get MP4 video |
-| GET | `/cache/{hash}/meta` | Get content metadata |
-| PATCH | `/cache/{hash}/meta` | Update metadata |
-| POST | `/cache/{hash}/publish` | Publish to L2 |
-| DELETE | `/cache/{hash}` | Delete from cache |
+| GET | `/cache/{cid}` | Get cached content (with preview) |
+| GET | `/cache/{cid}/raw` | Download raw content |
+| GET | `/cache/{cid}/mp4` | Get MP4 video |
+| GET | `/cache/{cid}/meta` | Get content metadata |
+| PATCH | `/cache/{cid}/meta` | Update metadata |
+| POST | `/cache/{cid}/publish` | Publish to L2 |
+| DELETE | `/cache/{cid}` | Delete from cache |
 | POST | `/cache/import?path=` | Import local file |
 | POST | `/cache/upload` | Upload file |
 | GET | `/media` | Browse media gallery |
@@ -185,7 +185,7 @@ Recipes are executed in three phases:
 ### Phase 1: Analyze
 Extract features from input files:
 - **Audio/Video**: Tempo, beat times, energy levels
-- Results cached by content hash
+- Results cached by CID
 
 ### Phase 2: Plan
 Generate an execution plan:
@@ -237,7 +237,7 @@ output: sync_video
 
 ### Local Cache
 - Location: `~/.artdag/cache/` (or `CACHE_DIR`)
-- Content-addressed by SHA3-256 hash
+- Content-addressed by IPFS CID
 - Subdirectories: `plans/`, `analysis/`
 
 ### Redis
@@ -318,12 +318,12 @@ Every render produces a provenance record:
   "task_id": "celery-task-uuid",
   "rendered_at": "2026-01-07T...",
   "rendered_by": "@giles@artdag.rose-ash.com",
-  "output": {"name": "...", "content_hash": "..."},
+  "output": {"name": "...", "cid": "Qm..."},
   "inputs": [...],
   "effects": [...],
   "infrastructure": {
-    "software": {"name": "infra:artdag", "content_hash": "..."},
-    "hardware": {"name": "infra:giles-hp", "content_hash": "..."}
+    "software": {"name": "infra:artdag", "cid": "Qm..."},
+    "hardware": {"name": "infra:giles-hp", "cid": "Qm..."}
   }
 }
 ```