Announce tick-inferred routines, opt-in and rate-limited (#247, #43)

The digestion tick already runs the pattern detector over all recorded
events (67563ed) and writes a proposed_routines row. What was missing is
the other half of #247: a proposal that nobody is at the mic for reaches
nothing but the /routines page, so a pattern noticed at 03:00 is only
seen if he goes looking.

This wires the tick's proposals into the existing care-delivery path
rather than a second channel: sev1 nudge, loop.Gate, dispatcher, same
routing table as an accepted routine. Restraints, since a feature that
speaks unprompted is the easiest way to turn Maven into a nag:

  - off unless configured — the new pattern_proposals block, absent by
    default, and deploy/mavend.json ships notify: false;
  - at most one announcement per tick however many patterns surfaced;
  - at most one per cooldown (24h default) across all pairs;
  - sev1, so quiet hours, away and snooze suppress it;
  - suppressed means dropped, not queued — /routines still has it;
  - once per pair for good, since proposed_routines is
    UNIQUE(action, object) and the row survives dismissal.

The body is pattern.PhraseRoutine's literal Russian, not LLM-worded, so
an inferred routine cannot arrive describing something never observed.

Also raises pattern.MinEvents from 3 to 4 — the interval-quality item on
#43. Two intervals with a ±50% band is a coincidence with a mean, not a
pattern, and now that a scan of all history can announce itself the cost
of a false positive is a permanent dismissal of that pair.

internal/config/config.go

@@ -140,6 +140,12 @@ type Config struct {
 	// item. See internal/morning for the evaluation engine. Empty ⇒ disabled.
 	MorningRoutines []MorningRoutineConfig `json:"morning_routines,omitempty"`
 
+	// PatternProposals — whether a routine the digestion tick inferred on its
+	// own may be announced, and how often. nil / absent ⇒ silent detection
+	// only: proposals are written for /routines and never announced. See
+	// PatternProposalConfig.
+	PatternProposals *PatternProposalConfig `json:"pattern_proposals,omitempty"`
+
 	// Praxis — the ecosystem attention-state service. When configured, maven
 	// calls the Praxis HTTP tools API for attention listing and item lifecycle.
 	// Maven never touches Praxis's database directly (ecosystem invariant: no
@@ -352,6 +358,40 @@ type DigestConfig struct {
 	SeverityCeiling int      `json:"severity_ceiling,omitempty"` // max sev batched
 }
 
+// PatternProposalConfig — announcement policy for routines the digestion tick
+// inferred by itself (Vikunja #247, #43).
+//
+// Detection is always on and always silent by default: the tick writes a
+// proposed_routines row and the /routines page shows it. Notify is what turns
+// "she noticed" into "she said something", and it is OFF unless configured —
+// Maven is not a nag and not autonomous, so a behaviour that speaks without
+// being asked has to be switched on deliberately, like weather and telegram.
+//
+// When Notify is on, the announcement is still heavily restrained:
+//   - at most one proposal per tick, however many were detected;
+//   - at most one per Cooldown across all pairs (not per pair), so a batch of
+//     freshly-detected patterns cannot turn into a queue of interruptions;
+//   - through the ordinary care-class gate (quiet hours / away / snooze), at
+//     sev1 — the lowest severity there is. A proposal is the least urgent
+//     thing Maven can say.
+//
+// A pair is only ever announced once, because it is only ever proposed once:
+// proposed_routines is UNIQUE(action, object) and the row survives dismissal.
+type PatternProposalConfig struct {
+	// Notify — announce newly inferred routines. Default false.
+	Notify bool `json:"notify,omitempty"`
+
+	// Cooldown — minimum spacing between two proposal announcements. 0 ⇒
+	// DefaultProposalCooldown (24h).
+	Cooldown Duration `json:"cooldown,omitempty"`
+}
+
+// AnnounceProposals reports whether inferred routines may be announced. Safe
+// on a nil receiver — an absent config block means silent detection.
+func (p *PatternProposalConfig) AnnounceProposals() bool {
+	return p != nil && p.Notify
+}
+
 // PhraserConfig — the LLM-backed phraser seam. The daemon spawns llama-server
 // as a managed subprocess and sends chat-completion requests to phrase nudge
 // and reminder messages. nil ⇒ the template-based Stub is used instead.
@@ -448,6 +488,11 @@ const (
 	DefaultLLMRouter = true
 
 	DefaultFactEnrichmentInterval = 30 * time.Second
+
+	// DefaultProposalCooldown — one inferred-routine announcement per day at
+	// most. A proposal is never urgent; if two patterns surface in the same
+	// hour, the second one waits, and the /routines page has it either way.
+	DefaultProposalCooldown = 24 * time.Hour
 )
 
 // Load reads the JSON config at path and applies defaults. A missing file is
@@ -520,6 +565,12 @@ func (c *Config) applyDefaults() {
 		c.Digest.SeverityCeiling = 2
 	}
 
+	// Absent block stays nil (⇒ silent detection). Present-but-partial gets the
+	// cooldown default, so `{"notify": true}` is enough to switch it on.
+	if c.PatternProposals != nil && c.PatternProposals.Cooldown <= 0 {
+		c.PatternProposals.Cooldown = Duration(DefaultProposalCooldown)
+	}
+
 	if c.Voice != nil {
 		if c.Voice.RouterThreshold <= 0 {
 			c.Voice.RouterThreshold = DefaultRouterThreshold