feat: rename include/index patterns to immutable/mutable with per-remote TTL

Replace the include_patterns/index_patterns split with a clearer
immutable_patterns/mutable_patterns model:

- immutable_patterns: artifacts cached indefinitely (no TTL)
- mutable_patterns: artifacts that expire and are re-fetched after
  cache.mutable_ttl seconds (replaces cache.index_ttl)

_PACKAGE_INDEX_PATTERNS renamed to _PACKAGE_MUTABLE_PATTERNS; all
built-in package-type index patterns (APKINDEX, repomd, manifests, etc.)
default to the remote's mutable_ttl (default 1 hour).

cache.file_ttl renamed to cache.immutable_ttl for consistency.
Adds github-archive remote to remotes.yaml as a worked example showing
tag archives as immutable and branch archives as mutable (1-day TTL).

docker-compose.yml: fix VERSION=dev → 2.2.2.dev0 (valid PEP 440),
add :z SELinux label to volume mounts.

tests/conftest.py

@@ -22,47 +22,47 @@ TEST_REMOTES = {
             "base_url": "https://dl-cdn.alpinelinux.org",
             "type": "remote",
             "package": "alpine",
-            "include_patterns": [".*/x86_64/.*\\.apk$"],
-            "cache": {"file_ttl": 0, "index_ttl": 3600},
+            "immutable_patterns": [".*/x86_64/.*\\.apk$"],
+            "cache": {"immutable_ttl": 0, "mutable_ttl": 3600},
         },
         "rpm-test": {
             "base_url": "https://example.com/rpm",
             "type": "remote",
             "package": "rpm",
-            "include_patterns": [".*/x86_64/.*\\.rpm$", ".*/repodata/.*$"],
-            "cache": {"file_ttl": 0, "index_ttl": 3600},
+            "immutable_patterns": [".*/x86_64/.*\\.rpm$", ".*/repodata/.*$"],
+            "cache": {"immutable_ttl": 0, "mutable_ttl": 3600},
         },
         "docker-test": {
             "base_url": "https://registry.example.com",
             "type": "remote",
             "package": "docker",
-            "cache": {"file_ttl": 0, "index_ttl": 300},
+            "cache": {"immutable_ttl": 0, "mutable_ttl": 300},
         },
         "docker-restricted": {
             "base_url": "https://registry.example.com",
             "type": "remote",
             "package": "docker",
-            "include_patterns": ["^library/nginx"],
-            "cache": {"file_ttl": 0, "index_ttl": 300},
+            "immutable_patterns": ["^library/nginx"],
+            "cache": {"immutable_ttl": 0, "mutable_ttl": 300},
         },
         "generic-test": {
             "base_url": "https://releases.example.com",
             "type": "remote",
             "package": "generic",
-            "include_patterns": [".*\\.tar\\.gz$"],
-            "cache": {"file_ttl": 0, "index_ttl": 0},
+            "immutable_patterns": [".*\\.tar\\.gz$"],
+            "cache": {"immutable_ttl": 0, "mutable_ttl": 0},
         },
         "custom-index-test": {
             "base_url": "https://example.com",
             "type": "remote",
             "package": "generic",
-            "index_patterns": ["metadata\\.json$"],
-            "cache": {"file_ttl": 0, "index_ttl": 600},
+            "mutable_patterns": ["metadata\\.json$"],
+            "cache": {"immutable_ttl": 0, "mutable_ttl": 600},
         },
         "local-test": {
             "type": "local",
             "package": "generic",
-            "cache": {"file_ttl": 0, "index_ttl": 0},
+            "cache": {"immutable_ttl": 0, "mutable_ttl": 0},
         },
     }
 }