feat(auth-jwt): initial implementation — JWT lifecycle and AuthMiddleware (v1.0.0)

Introduces code.nochebuena.dev/einherjar/auth-jwt — JWT authentication middleware
and token lifecycle management for the Einherjar framework. Absorbs httpauth-jwt
from micro-lib with three changes: logger parameter on AuthMiddleware, httputil.Error
for consistent 401 responses, and added ECDSA support.

Signers and Verifiers (one file per implementation — CT-6 compliant):
- Verifier interface — Verify(tokenString string) (*jwt.Token, error)
- Signer interface — extends Verifier; adds Sign(claims jwt.Claims) (string, error)
- signer_hmac.go — NewHMACSigner(secret) → HS256; jwt.WithJSONNumber() on Verify
- signer_rsa.go — NewRSASigner(key) + NewRSASignerFromPEM(pem) → RS256
- verifier_rsa.go — NewRSAPublicKeyVerifier + NewRSAPublicKeyVerifierFromPEM → RS256 verify-only
- signer_ec.go — NewECSigner(key) + NewECSignerFromPEM(pem) → ES256/384/512; algorithm
  auto-detected from key curve (P-256→ES256, P-384→ES384, P-521→ES512)
- verifier_ec.go — NewECPublicKeyVerifier + NewECPublicKeyVerifierFromPEM → EC verify-only

Token lifecycle:
- TokenConfig struct — AccessTTL, RefreshTTL, Issuer
- TokenPair struct — AccessToken, RefreshToken, ExpiresIn
- IssueTokenPair — access + refresh pair; customClaims merged at top level; refresh
  carries only sub/iss/iat/exp/jti/fam; jwt.WithJSONNumber() preserves int64 bitmasks
- Blacklist interface — IsRevoked + Revoke; satisfied by cache-valkey via duck typing
- ErrTokenRevoked — errors.New sentinel; errors.Is pattern for replay-attack detection
- RefreshTokenPair — verifies token, checks blacklist, revokes old JTI, issues new pair

HTTP middleware:
- AuthMiddleware(logger, verifier, publicPaths) — verifies Bearer tokens; calls
  authmw.SetTokenData on success; 401 routed through httputil.Error (Warn level);
  publicPaths use path.Match wildcards; accepts Verifier (not Signer) to enforce
  narrowest-interface principle for verify-only services

Compliance test (package authjwt_test) enforces CT-6 (≤1 exported TypeSpec/file),
compile-time interface satisfaction, and behavioural coverage: HMAC/RSA/EC sign+verify,
algorithm mismatch rejection, IssueTokenPair claims/jti/fam, RefreshTokenPair success/
revoked/blacklist-error/custom-claims, MaxInt64 json.Number precision, AuthMiddleware
valid/invalid/expired/missing/public-path/wildcard/JSON-body/RSA-verifier/SetTokenData.

Depends on auth v1.0.0, contracts v1.0.0, core v1.0.0, web v1.0.0, jwt/v5 v5.2.1.

- identifiable.go: package-level Module variable (observability.Identifiable) for version
  identification — auth-jwt is a function library; not registered with the launcher

.gitea/CODEOWNERS

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+* @einherjar/CoreDevelopers @einherjar/Agents

.gitea/pull_request_template.md

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+## Summary
+
+<!-- One or two sentences: what does this PR do and why? -->
+
+---
+
+## Type of change
+
+- [ ] Bug fix — non-breaking change that resolves an issue
+- [ ] New feature — non-breaking addition of functionality
+- [ ] Breaking change — alters existing behavior or public API
+- [ ] Documentation update
+- [ ] Refactor — no functional change, no new API surface
+- [ ] Test improvement
+
+---
+
+## Description
+
+<!--
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+- What problem does this solve?
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+- Were there alternatives you considered and rejected?
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+
+---
+
+## Testing
+
+- [ ] I added or updated tests that cover my changes
+- [ ] All tests pass locally — `go test ./...`
+- [ ] No formatting issues — `gofmt -l .` produces no output
+- [ ] No vet warnings — `go vet ./...` is clean
+
+---
+
+## Checklist
+
+- [ ] At most one exported type per non-test `.go` file (CT-6)
+- [ ] No new external dependencies added without prior discussion in an issue
+- [ ] Public API changes are reflected in `CHANGELOG.md`
+- [ ] Breaking changes include a migration note in the PR description above
+
+---
+
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